Dave Hubble's ecology spot

Oh, my rusty hollyhocks!

2012-03-15T11:14:00.000Z

As my wife knows, I don't have to be at work to get distracted by an interesting bug, plant or fungus. So, nobody was very surprised when, during a leisurely walk following a family pub lunch yesterday, I bent down to take a sample of an interesting-looking hollyhock (Alcea rosea) leaf.

Hollyhock leaf showing orange fungal structures and something small indicated by a red arrow...

As you can see from this photo, the leaf bears numerous orange fungal structures on both the blade and petiole (stalk), plus there's a small invertebrate indicated by the red arrow. Staring with the fungus, a closer look highlights some familiar structures...

Elongate orange fungal structures on the petiole. These are blister-like and the dark orange masses are spores that have become exposed as the blisters have ruptured.

On the leaf blade, similar (but more globular) spore-filled structures are seen (red arrows), while some appear greyer in colour (blue arrow).

Although small, these blisters clearly include some abnormal growth and colouration of the plant's tissues and thus can be considered to be galls. A quick look in Redfern & Shirley (2011) provides an easy identification - there is a single galling species species found on hollyhock (and some other Malvacaeae), the rust fungus Puccinia malvacearum. This specimen clearly matches the description, including the grey colour of older spores. Although this species may be unfamiliar, the genus is found on many plants with those on lords-and-ladies (Arum maculatum) and nettles (Urtica dioica) being particularly common and widespread - just look out for the little orange rings and pustules. Now onto the potentially trickier tiny invertebrate...

Small (3 mm long) leafhopper on the hollyhock leaf. See below for the meaning of the red arrows and circle.

If you are familiar with generalist insect books such as Chinery (1986), you can quickly tell that this is a leafhopper (Cicadellidae) of some sort, possibly a relative of the often-illustrated Eupteryx aurata. However, there are numerous species in this group (the subfamily Typhlocybinae) and the more technical Le Quesne & Payne (1981) may well be needed to identify them by keying out. So, back to a bit of taxonomic morphology - important diagnostic features are as follows:

The three apical forewing veins (indicated by red arrows in the above photo) join the same cell (indicated by the red circle), noting that two of the veins merge to form a 'Y'.
In the same photo, you can see the white 'waxy area' on the front edge of the forewing. Just behind thisthere is an irregularly shaped black spot cut into two by a pale wing vein. In some species this spot marges into one.
In side view the front of the face (running down to the piercing mouthparts) is flat without a clear angle part of the way down (see top photo below).
The pattern on the pronotum is distinctive - two clear black dots near the front edge with fuzzy longitudinal brown marks attached to them, plus other smaller black dots to the sides (see lower photo).
The pattern on the head shows a triangle of three large black spots; the single rear spot does not have a dent in its front edge.
The front of the 'face' is not clearly shown here, but in the above photo you can just see that there are two more black spots in front of the three on the head, but not another pair further to the side by the eyes.

Side view of the leafhopper showing the flat front to the 'face'.

More-or-less dorsal view of the leafhopper showing the patterns on the head and pronotum.

Combining these features and using them in the key, the species can be identified as Eupteryx melissae. This is a leafhopper which, like the rust fungus above, is known from hollyhocks and related Malvaceae. It is very similar to E. thoulessi but can be separated using the features on the front of the face (E. thoulessi has the extra pair of lateral spots near the eyes which are absent here), and of course the food-plant is a helpful clue. Although this specimen was seen in mid-March, it is usually not recorded until May. However, it may have emerged following a recent spell of warm weather; when collected it appeared dead, but was probably simply torpid as the temperature had fallen considerably over a couple of days - certainly it became active again under the microscope.

More soon...

References

Chinery, M. (1986). Collins Guide to the Insects of Britain and Western Europe. Collins, London.
Le Quesne, W.J. & Payne, K.R. (1981). Cicadellidae (Typhlocybinae) with a checklist of the British Auchenorhyncha (Hemiptera, Homoptera). Royal Entomological Society Handbooks for the Identification of British Insects 2(2c): 1-95.
Redfern, M. & Shirley, P. (2011). British Plant Galls (2nd ed.). FSC, Shrewsbury.

Antscape: ghosts in the graveyard

2012-03-09T14:42:00.001Z

Despite the title, it's early March and so couldn't be much further from Halloween, but wildlife respects its own calendar, not ours... Anyhow, having gone for a wander in the woods a few days ago, I took my usual shortcut through the nearby churchyard and noticed something intriguing. On many of the graves, especially on the corner-stones, tussocks of soil and grass had developed. I must have seen this dozens of times before but it had never really grabbed my attention - this time however, I stopped to take a closer look...

Tussocks on the corners of a grave.

From a distance, these tussocks just look like long grass that the mower has missed. However, close up it is clear that they are actually formed of fairly loose soil with grass and moss growing on it. Like any good ecologist, I began to delve...

Yellow Meadow Ants (Lasius flavus) in a churchyard 'tussock'

As soon as pulled open one of these tussocks, it was clear how they had formed - they are actually anthills of the Yellow Meadow Ant (Lasius flavus). L. flavus is a common species, associated with the formation of 'antscapes' comprised of hundreds of closely spaced anthills on undisturbed grasslands (although sometimes they don't form anthills). In Britain it is the only species building long-term nests of the 'unthatched mound' type - a couple of others such as L. niger produce occasional small, temporary mounds, while the Wood Ant Formica rufa produces much bigger mounds covered ('thatched') with bits of twig etc. (Skinner & Allen 1996). L. flavus nests are up to about 30 cm tall, the mound effectively being the spoil heap from soil dug out when the colony builds its underground nest of tunnels and chambers. Being subterranean, L. flavus is rarely seen unless sought out, despite probably being Britain's commonest ant - the underground habit has led to reduced eye development and even soil is brought to the surface at night (Pontin 2005), so daytime activity is unlikely to be seen in passing - certainly I saw no ants on the surface. This also keeps different species apart - in this case, L. flavus lives in the same areas as L. niger, but the latter lives on the surface forming much larger territories (active L. flavus mounds can be as little as 2 m apart, below which inter-colony competition is too intense and queens are attacked prior to establishment of a new colony) (Pontin 2005). As the ants cannot make mounds in mowed (or heavily grazed) areas, it is clear that their use of the graves as a focus for their anthills allows them to avoid disturbance by mowers. In meadows, I have seen newly forming nests being built around plant stems - possibly to provide an initial scaffolding for the loose soil particles.

Like many ant species, L. flavus feeds on the sugary 'honeydew' produced by aphids that are tended by the colony. However, the ant-aphid relationship is more complex than this as L. flavus has 'collected' a number of subterranean aphid species (e.g. of the genera Forda, Geoica, Aphis, Tetraneura and Baizongia) which, in Britain, have lost their sexual generation associated with woody plants and are now entirely asexual on the roots and stolons of grasses. Others such as Sappaphis bonomii lay over-wintering eggs on plants above ground, and L. flavus tends them as if they were ant eggs (at the wrong time of year). Not only that, but as well as using aphids as sources of honeydew, L. flavus also uses them as prey to feed its larvae (Donisthorpe 1927, Pontin 2005). The aphids rarely disperse openly above ground level, suggesting that despite the possibility of being eaten by ant larvae, the protection of subterranean ants outweighs this risk. Further, this may effectively form a type of 'culling', keeping aphid density below levels where they tend to start producing winged forms for dispersal.

So, although this is a common and widespread species, it hides a symbiotic lifestyle that is rarely seen despite taking place beneath our feet as we walk across many an old pasture or other undisturbed grassland. I'm certainly tempted to ask permission to investigate these churchyard mounds more closely and maybe learn more about the aphids and other 'guest' invertebrates that can be found within. As the church (St. Mary's, Bishopstoke) was consecrated in 1891, there has been plenty of time for the ant community to develop. Lastly, I want to look briefly at the landscape, or 'antscape', effects of L. flavus. In an old pasture, the anthills are close together (active ones may abut or overlap old inactive ones), but their arrangement is effectively patchy and random. In the churchyard, the association with graves means that this is not the case and the anthills are arranged more or less in a grid matching the positions of graves - even where these have since disappeared - in such cases the pattern of anthills marks the outlines of old graves - ghosts in the graveyard!

Pattern of L. flavus anthills following the locations of current and missing graves.

References

Donisthorpe, H.St.J.K. (1927). Guests of British Ants. Routledge, London. [An old classic; can be a bit expensive, and a lot of the taxonomy has changed, but still worth having].
Pontin, J. (2005). Ants of Surrey. Surrey Wildlife Trust, Woking. [Maps of ant distribution in Surrey, but plenty of other more widely applicable information about British ants].
Skinner, G.J. & Allen, G.W. (1996). Ants. Richmond, Slough. [An excellent little book in the Naturalists' Handbooks series. Includes species-level keys to the British ant fauna. If you want just one book on British ants, I recommend this].

Further reading

Agosti, D., Majer, J.D., Alonso, L.E. & Schultz, T.R. (2000). Ants. Standard Methods for Measuring and Monitoring Biodiversity. Smithsonian, Washington DC. [Takes a global approach with particular emphasis on the tropics and Americas, but covers a range of widely applicable techniques and ideas].

Hampshire's newest slug, a lover of logs

2012-03-04T15:22:00.002Z

Yesterday at the annual HBIC Recorders' Forum, local members of the Conchological Society brought a display stand including a live specimen of Limacus maculatus. This was found in the Lyndhurst area of the New Forest and represents a species new to Hampshire as of 2011.

Limacus maculatus

L. maculatus (previously in the genus Limax as is the case in many key British texts) is also known as the Irish Yellow (sometimes Green) Slug; it is widespread in Ireland (see map) where it is found commonly in towns and gardens as well as being associated with rotting wood in natural habitats (NMNI 2010). emerging at night to feed and climb. It is medium to large (70-130 mm long), yellowish to greenish and blotchy, with grey to blue-grey tentacles and colourless to yellow or orange slime. A common pattern variation has the darker mottling more fragmented such that the animal has a spotty appearance, similar to that of Limacus flavus (the Yellow Slug) which is similarly often given as genus Limax. These two species were previously considered to be the same (Cameron et al. 1983), though L. flavus is usually a paler yellowish colour and spotty, with a pale zone extending above the fringe of the foot whereas in L. maculatus there is dark pigmentation to the fringe of the foot, and the animal usually has larger dark blotches (though note the spotty variant mentioned above). As a rule of thumb, though care is needed as they are variable, L. maculatus is usually a darker and blotchier green while L. flavus is usually a paler and spottier yellow. See here for photographs of extended specimens showing the tentacles.

More widely, as well as Britain, it is known from France, the Canary Isles, Romania, Bulgaria, Ukraine, Russia, the Black Sea coast and the mountains of Transcaucasia (Turkey to Azerbaijan and NW Iran). Its full distribution is not known with certainty (Kerney, 1999), though it is considered to have been introduced by humans into the British Isles (as well as around Moscow and St. Petersburg), with its native range being the deciduous forests of the Crimea and Caucasus (Wiktor & Norris 1982, Sysoev & Schileyko 2009, Schütt 2010).

In Britain, most records of L. maculatus (see map) are from northern England, with a scattering elsewhere. While L. flavus is largely associated with humans (garden rubbish, damp cellars and outbuildings etc) with occasional records in woodland, L. maculatus is more strongly associated with woodlands, particularly beneath large logs, bark or in tree-holes where moist conditions are maintained (although it can be found in situations similar to those of L. flavus, as well as under stones in fields). The Hampshire specimens seemed to be associated particularly with large logs. Though found sometimes on rubbish, food put out for other animals, dead plants, or on lichens on walls and stones (Cook & Radford 1988, Schütt 2010), its strong association with large logs means that L. maculatus probably feeds on wood-decay fungi, suggesting that large fallen timber may provide both food and shelter. This diet (fungi, algae, lichens, dead plant material) is common among slugs and although many gardeners and vegetable growers dislike slugs, only a few species such as the common Field Slug Deroceras reticulatum actually feed on living higher plants (Kerney & Stubbs, 1980).

As a final note, the 'new to Hampshire' tag is a close one as it was found in Christchurch in 1884 (Kerney 1986) - though now in the county of Dorset, back then the town was in Hampshire...

Found L. maculatus in Britain? Let your local Biological Records Centre know...

References

Cameron, R.A.D., Eversham, B. & Jackson, N. (1983). A field key to the slugs of the British Isles. Field Studies 5: 807-824.
Cook, A. & Radford, D. J. (1988). The comparative ecology of four sympatric limacid slug species in Northern Ireland. Malacologia 28: 131-146.
Kerney, M. (1986). A 19th-century record of Limax maculatus in the British Isles. Conchologists' Newsletter 97: 361.
Kerney, M. (1999). Atlas of the Land and Freshwater Molluscs of Britain and Ireland. Harley, Colchester.
Kerney, M. & Stubbs, A. (1980). The Conservation of Snails, Slugs and Freshwater Mussels. NCC, Shrewsbury.
National Museums Northern Ireland (2010). MolluscIreland: Limacus maculatus (Kaleniczenko 1851) Irish Yellow Slug. [accessed 04/03/2012]
Schütt, H. (2010). Turkish Land Snails. Verlag Natur & Wissenschaft, Solingen.
Sysoev, A. & Schileyko, A. (2009). Land Snails and Slugs of Russia and Adjacent Countries. Pensoft, Sofia.
Wiktor, A. & Norris, A. (1982). The synonymy of Limax maculatus (Kaleniczenko, 1851) with notes on its European distribution. Joural of Concholology 31: 75-77.

Quadrennial nature - a leap-year listing

2012-02-29T16:51:00.000Z

I'm not investigating anything deep and meaningful today (well, not much anyway) - as it's February 29th, I thought I'd post up some examples of natural events that also happen once every four years (i.e. quadrennially), just to see what's out there...

The first example is animal-based, but not strictly natural - during Inca times, vicuña (Vicugna vicugna, relatives of llamas) were sheared and then released during a herding event called a chacu, held once every four years. As vicuña produce about 500g of wool per year, a lot of animals were needed to make more than a few socks and scarves...

A vicuña in Peru; thanks to Alexandre Buisse for putting this image in the public domain.

Female gorillas produce young about once every four years - about the same time that a young gorilla stays with its mother. A silverback male will look after an orphaned youngster as long as it has been weaned. More here.

Similarly, female African bush/savannah elephants Loxodonta africana breed every four years...

...and so do North American bears.

Lemming (rodents in the genera Dicrostonyx, Lemmus, Myopus and Synaptomys) populations crash every four years or so - the reasons are not fully understood (it may be to do with a combination of predation, food supply and seasonal conditions such as winter length - more info on the 'Lemming Cycle' here), but when lemming numbers are low, the spectacular Snowy Owl (Bubo scandiacus) is more likely to move south, being seen in areas where it is not usually found, including northern areas of Britain - very exciting for bird-watchers! Arctic fox (Vulpes lagopus) populations also appear to peak in reponse to high lemming prey numbers, but foxes can't fly to Britain when food is scarce.

In the western states of the USA, wild horse herds can double in size around once every four years. For this reason, the Bureau of Land Management publishes and implements its Policy Handbook on Wild Horse and Burro Management.

Salmon runs in North America can be impressive autumn events is one of the largest in North America. One of these, in the Adams River of British Columbia, Canada, is particularly large with peak 'dominant years' about every four years. These are marked by the quadrennial 'Salute to the Sockeye' festival.

There are other examples in nature, but in human society, many activities follow a four-year cycle for reasons of tradition and the practicalities of organising large events such as the Olympics and the Football World Cup. This tendency towards four-year cycles sometimes affect wildlife - for example, tiger surveys in India were undertaken every four years, but it has become clear that changes in tiger populations can occur over the course of a single year. This means that important population changes, and the causes of them, could be missed and there is now movement towards more appropriately frequent annual monitoring. Other event such as the Sockeye Salmon festival mentioned above are quite different, with human activities being driven by natural cycles - as it should be. Happy Leap Day!

Bark at the Moon - small invertebrates of timber (Part 6)

2012-02-27T15:51:00.000Z

It's been a while since my last post about the small invertebrates that have made their home in our firewood store. These have generally been small beetles (Coleoptera) and barkflies (Psocoptera), but this one - found wandering along the coffee table just after a load of logs had been brought in belongs to a group I sometimes neglect a little (generally because of my tendency to favour the beetles); the true bugs or Hemiptera.This one was about 7mm long with striped legs and connexivium (the sides of the abdomen) and a hairy pronotum. These features, along with the overall appearance, indicate that this is the Nettle Groundbug Heterogaster urticae, one of the Lygaeidae (groundbugs).

Dorsal view of Heterogaster urticae

H. urticae is a common species in southern England - found on nettles in more open habitats during the summer, adults overwinter in various places, including in hollow stems and beneath bark which is likely source of this specimen which has now been placed back in the detritus in our woodstore. Adults emerge in the spring and then mate. The hairy pronotum and series of tibial stripes separate this species from the similar, though less widely distributed, H. artemisiae (Southwood & Leston, 2005). For more images, including nymphs, see here. As ever, it can be interesting to zoom in on some of the detail:

Head of H. urticae showing the bulbous compound eye, and to its left, the small, shiny red-pink simple eye or 'ocellus'.

The pale, erect hairs on the pronotum of H. urticae. The coarse punctures in the pronotal surface are also visible.

That's all for now - a fairly short post today - more soon...

Reference

Southwood, T.R.E. & Leston, D. (2005). Land & Water Bugs of the British Isles. Pisces, Newbury. Edited facsimile of the 1959 work.

Wheels of life

2012-02-23T17:25:00.001Z

Straight in with a question today - have wheels evolved in nature? Now, I know it's been written about before, and there's no shortage of discussions on any number of online forums (or fora if you prefer), but it's something I've been musing on and coming up with some underlying questions - so, here goes with one my rare forays into the more speculative realms of biology and ecology...

Firstly, why might wheels be a useful adaptation? Well, they could provide an efficiency and simplicity of motion in some circumstances - I can certainly imagine animals using wide wheels to trundle across the soft sediments of the ocean floor for example (much like the wire-wheeled lunar rovers from Apollos 15-17). However, legs and fins generally work pretty well, with wheels really coming into their own on straight, smooth, hard surfaces. These are not common in nature, though humans produce plenty of them - and hence plenty of wheels. So, a lack of evolutionary advantage might be one reason why natural wheels are not widely seen.

Secondly, what do I even mean by a wheel? Here, I am only considering something that has an axle or bearing. There are plenty of organisms that roll - the South American pebble toad Oreophrynella nigra that tumbles down slopes to avoid predation, the wide variety of tumbleweed plants (and the rarer 'tumblefruits' such as Physaria) that disperse seeds as they roll with the wind, and the puffballs of the genus Bovista that are also blown around and so disperse their spores more widely. Ocean currents roll the coral Porites lutea across the sea floor and the small stomatopod mantis shrimp Nannosquilla decemspinosa can curl up and roll slowly like a wheel if stranded on a shallow damp sandy shore, thus returning to the sea. These are all interesting in their own right, and there are other examples, but none of them are wheels.

In fact, there don't appear to be any organisms that roll along on wheels in the way that humans' various vehicles do. As mentioned above, there may simply be no evolutionary pressure to produce a wheel, but there are also developmental constraints. For example, to have a wheel in a multicellular organism is tricky because, to be able to rotate freely, the wheel needs to be detached from the rest of the organism. If this is the case, how could it maintain a blood supply, neural connections and so on? Two options come to mind:

1. The wheel could be made of 'dead' material secreted by the organism, such as carapace material. This could grow as a toroid (doughnut-shaped) swelling on a limb/axle and gradually separate by thinning near the limb. This could produce a passive wheel on an axle much like a wood-turner produces a freely movable (but not removable) ring from a single piece of wood.
2. The wheel could be alive but self-contained. If a ring of cells developed as above and then detached, to be an effectively autonomous wheel, it would have to have its own energy supply (photosynthesis, chemosynthesis?) and so on.

Neither of these options have been discovered in nature, though this does not mean they never will - my feeling is that the lack of need is more likely to prevent wheels evolving than developmental problems. So far, I have not differentiated between passive and active wheels i.e. whether they simply roll like a cart (reducing the friction that would be caused by dragging) or are actively rotated by an energy source. Active wheels are developmentally even more problematic as a torque needs to be applied - in animals, motive force is produced by muscles, but this would not work on wheels as they need to be freely rotating. However, in bacteria, the problems of producing motive force, overcoming inertia and so on have been solved. In fact, the only example discovered so far of a true biological wheel (an active one that produces continuous propulsive torque around a fixed structure), is the bacterial flagellum, the a propeller-like thread used for locomotion. Where the flagellum enters the cell membrane, there is a motor protein that works like a rotary engine, powered the flow of hydrogen ions (i.e. protons) across the bacterial cell membrane down a concentration gradient created by a proton pump. A similar system using a sodium ion pump exists in the genus Vibrio.

The structure of the flagellar base showing cutaway details of the 'motor'. Thanks go to Mariana Ruiz Villarreal for putting this and other diagrams in the public domain.

At an even smaller scale, the enzyme ATP synthase (which is involved in energy storage and transfer within cells) is somewhat similar to bacterial flagellar motors and is likely to be an example of modular evolution i.e. where two separate structures or sub-units (which evolved and previously functioned separately) become joined or associated, and in doing so gain a new function.

So, although true wheels have not been discovered in multicellular organisms, and both developmental and utility constraints make their evolution highly unlikely, maybe impossible, there are ways that wheels might be used in nature:

1. Through symbiosis, joining two otherwise unrelated structures/organisms in order to get round the developmental problems preventing direct evolution of wheels. This could be instinctive (imagine an extension of dung-ball rolling by dung-beetles) and is an idea which has been explored in fiction, e.g. in the Amber Spyglass (Philip Pullman, 2000). In this book, an alien race known as the Mulefa use large, round seed pods as wheels. They put these on sideways-oriented claws (which act as axles) on two of their legs, using the other two legs to push themselves along. The symbiotic aspect occurs because the trees that produce the seed pods depend on the rolling action under the weight of the Mulefa to break open the pods and allow the seeds to disperse and germinate. A number of other science fiction novels consider biological wheel use in a variety of ways, but Pullman's is probably my favourite so far, though other examples include David Brin's Brightness Reef (1995) and Infinity's Shore (1996), and Wheelers (2000), co-authored by Ian Stewart and Jack Cohen (who happen to be a couple of Terry Pratchett's collaborators if you like a bit of nerd-trivia).
2. Through tool use. Humans do this, using wheels widely - could other species do the same, even if with less technological sophistication? I'm just waiting to see corvids start rolling past...

OK, I think that's enough speculation for one day - if anyone out there does know of other examples of 'bio-wheels', I love to hear about them, so feel free to add a comment.

OMG in the OMZ: massive marine microbes

2012-02-15T16:37:00.001Z

Today, I'm drawing inspiration from the Census of Marine Life, a decade-long project which has produced a huge inventory of marine life - a baseline catalogue to be used for further research and to inform the management and conservation of marine life. The Census looked at all scales from microbes to whales, at all latitudes and at all depths. The Census has produced a range of books, both popular and technical - one of the most straightforward and non-specialist, 'Citizens of the Sea' (Knowlton 2010) provided a couple of snippets that induced me to delve into the detail rather more...

First up, megabacteria - not the disease of budgies (which is actually a yeast), but very large true bacteria discovered off the coast of Chile and Peru in the 1960s. Placed in the genus Thioploca, the bacteria are filamentous and 2 to 7 cm (yes, cm) long. Secreting mucus, they form vast mats (the largest covering 130,000 km-sq) in/under the 'oxygen minimum zone' (OMZ), an area at 40-280 m with very little dissolved oxygen; instead they have to rely on hydrogen sulphide in the sediments. They oxidise this using nitrates (from sea water) which they can concentrate up to 500 mM in the liquid vacuole that occupies over 80% of their cell volume, even though the concentration of nitrates in sediment is only around 25 μM. Mucus-sheathed transport filaments send this nitrate 5–10 cm down into the sediment and reduce it, thus oxidising the hydrogen sulphide and creating a coupling of the nitrogen and sulphur cycles in the sediment (Fossing et al. 1994), producing pyrite and elemental sulphur as a result (Ferdelman et al. 1997). Thus, organic matter (in the form of anaerobic dissolved organic carbon) can be oxidised at low oxygen concentrations. The mats also provide food and shelter for a range of animals including squat lobsters (Pleuroncodes monodon), amphipods, and ophiuroids (Grupe 2011). As the OMZ shares features with conditions during the Proterozoic period (2.5 bya to 650 mya), and similar microfossils have been found, such bacteria may provide an insight into ancient life forms and ecology as well as performing a still little-known but key function in nutrient cycling. Research is ongoing with one recent example investigating Thioploca found in Danish waters where (in the species T. ingrica) nitrate accumulation was lower at around 3 mM, with bicarbonates and acetates used as carbon sources, and no mat being formed (Høgslund et al. 2010).

A core from a Thioploca bacterial mat. The core is about 8 cm across and the mat about 1 cm thick. The mat is made up of many bacterial filaments with individual cells visible to the naked eye as white threads. Huge for bacteria! Photo courtesy of NOAA/Lisa Levin.

Now, ocean acidification due to carbon emission from fossil fuels may affect marine microbes - with microbial ecosystems responsible for between 50 and 90% of all marine biomass and over 95% of marine respiration, they maintain Earth's habitability though their influences on climate (they can sequester atmospheric carbon dioxide), nutrient cycling and the decomposition of pollutants (Leahy 2012). So, this could be very serious indeed and current research is looking at the sensitivity of marine microbes to acidification. If I find links to results from this research, I'll post an update, plus I have some more bacterial and marine posts (among others) in the pipeline.

References

Ferdelman, T.G., Lee, C., Pantoja , S., Harder , J., Bebout , B.M. & Fossing, H. (1997). Sulfate reduction and methanogenesis in a Thioploca-dominated sediment off the coast of Chile. Geochimica et Cosmochimica Acta 61(5): 3065-3079. Fossing, H, Gallardo, V.A., Jørgensen, B.B., Hüttel, M., Nielsen, L.P., Schulz, H., Canfield, D.E., Forster, S., Glud, R.N., Gundersen, J.K., Küver, J., Ramsing, N.B., Teske, A., Thamdrup, B. & Ulloa, O. (1994). Concentration and transport of nitrate by the mat-forming sulphur bacterium Thioploca. Nature 374: 713-715.
Grupe, B. (2011). Sea Floor Habitats of the Chile Margin. NOAA Ocean Explorer [accessed 15/02/2012].
Høgslund, S., Nielsen, J.L. & Nielsen, L.P. (2010). Distribution, ecology and molecular identification of Thioploca from Danish brackish water sediments. FEMS Microbiology Ecology 73(1): 110-120.
Knowlton, N. (2010). Citizens of the Sea: Wondrous Creatures from the Census of Marine Life. National Geographic, Washington DC.
Leahy, S. (2012). Giant Bacteria Colonize the Oceans. Tierramérica. [accessed 15/02/2012].

Antarctic sea spiders: polar or abyssal gigantism?

2012-02-09T15:03:00.001Z

It is well known that in certain situations, some species evolve to be unusually large members of their taxonomic groups - the phenomenon of gigantism. Two such situations are polar and abyssal (deep-sea) gigantism, but why do large species evolve in polar and/or deep sea waters? As we will see, the answers are not always straighforward and are not necessarily the same for both situations. To illustrate this, I want to look at sea-spiders - not actually spiders but marine arthropods in the class Pycnogonida. A brief but informative introduction to this group can be found here, but in summary they are mostly free-living and are found at all latitudes and ocean depths. Superficially resembling spiders (though their taxonomic link to other groups is unclear), they have a cephalon (head) and a 4- (sometimes 5- or 6-) segmented body, each segment with a pair of walking legs (the rear segment bears a small abdomen), while the cephalon has various feeding appendages and palps, plus in males a pair of ovigers (leg-like appendages primarily used for carrying eggs & caring for young, but also for cleaning and courtship) which are found only in the Pycnogonida. Males also have 'cement glands' which they use to form eggs into round masses that are carried on the ovigers (Barnes 1980). Their biology is poorly studied - see Arnaud & Bamber (1987) for a useful review - but they reproduce by hatching as larvae or post-larvae with some being dispersed by medusae (jellyfish) and appear to feed on sessile animal prey or algae. Having such small bodies, their guts extend into their legs and in females, eggs are carried inside the femora. Around Britain, one common sea-spider is Pycnogonum littorale, a temperate shallow-water species (distribution given here) with a body around 5mm long and hence a leg-span of around 20mm.

A display of Pycnogonum littorale at the OUMNH

In contrast, polar and/or deep-water species may have leg-spans up to 750mm, especially in the family Colossendeidae.

Colossendeis wilsoni, A large Antarctic sea-spider also in the OUMNH collection. For scale, the label font is the same size as in the photo of P. littorale above.

So, why this gigantism in polar and abyssal marine environments? As noted in the excellent Deep Sea News, it is unclear whether the cause is the same in both cases, and the two tend to be confused in scientific reporting by the media. Also, although giant sea-spiders are familiar examples of Antarctic gigantism, many are found in deep water and therefore a species may be subject to the processes of adaptation to both polar and abyssal conditions, making it difficult to separate the two effects. For example, specimens of C. wilsoni (photo above) in the Smithsonian Museum were found at depths between 36m and 801m, while the most common Antarctic species in this genus, C. megalonyx, has been found between 3m and 4,900m (Wu & Mastro 2004)! Hence, it is not clear whether gigantism in this species is polar or polar-and-abyssal.

A widely cited paper by Chapelle & Peck (1999), found that the maximum size of amphipods (shrimp-like crustaceans) was related to dissolved oxygen rather than temperature or salinity, with polar waters being high in dissolved oxygen, because water can hold more oxygen at low temperatures. Similar effects in bivalve molluscs have also been found (e.g. Pörtner et al. 2006). The reasoning behind this 'oxygen hypothesis' is that as the size of an organism increases, its surface area:volume ratio reduces. This means that larger animals have more tissue volume requiring oxygen, but relatively less surface area with which to sequester it from the surrounding water. In warmer waters, not only is their less dissolved oxygen, but the oxygen needs of animal tissues is higher. Thus polar gigantism occurs due to cold water temperatures and high levels of dissolved oxygen. However, more recent research involving the self-righting abilities of 12 different-sized species of sea-spider (Woods et al. 2008) did not fully support the oxygen hypothesis, although it did agree that oxygen availability was likely to be one important factor, just not the only one. A possible explanation is that, being an apparently early branch of sea-spider evolution (Arango & Wheeler 2007), Colossendeis species have been adapting to cold, well-oxygenated waters for a longer period that other genera and have oxygen delivery systems which are more finely tuned to such conditions. If this is the case, then climate change is a potentially serious threat to a specialist groups of species functioning with narrow oxygen safety margins i.e. warmer waters leading to higher oxygen demand and lower availability could push Colossendeis beyond these margins more quickly than it can adapt.

So, although it seems that polar gigantism is a result of oxygen availability plus other factors, abyssal gigantism is in some ways more mysterious. Firstly, as noted by Deep Sea News, much work has looked at deep sea dwarfism rather than gigantism because so many taxa show this reduction in size, suggesting that the deep ocean is primarily a small-organism habitat (McClain et al. 2005, Kaariainen & Bett 2010). Thus, the incidence of abyssal gigantism (seen particularly in crustaceans, but also a range of other taxa) contrasts strongly with what appears to be the 'normal' situation in the deep ocean.

Abyssal dwarfism has generally been attributed to low food availability, with most animal communities (away from seeps and vents) relying on the 'marine snow' of detritus sinking from the surface, with occasional larger localised inputs such as dead whales. Thus little food arrives, especially away from productive shallow coastal waters. However, several possible explanations for the rarer gigantism have been proposed e.g.:

Higher oxygen availability (Chapelle & Peck 2001) as the amount of available oxygen determines the amount of sustainable tissue, with cell size and number both increasing with higher oxygen concentration in Drosophila fruit flies (Frazier et al. 2001) and freshwater amphipods (Peck & Chapelle 2003). In gastropods, a link between larger size and more oxygenated deep-sea sites has been noted (McClain & Rex 2001), but giant isopods Bathynomus sp. are known from low-oxygen regions in the Gulf of Mexico.
Longer lifespans due to reduced predation (few predators) and slower growth rates in cold water with larger cell size in crustaceans (Timofeev 2001) with a similar process suggested for other taxa (e.g. Van Voorhies 1996).

However, although key effects such as the link between oxygen levels and cell size/number have been described, these are the result of work on unrelated taxa and it remains unclear precisely why Colossendeis sea-spiders (let alone giant isopods) should exhibit gigantism while others do not - and so it is tie for a little (hopefully not too idle) speculation:

Through development of fat reserves, larger size may allow longer gaps in feeding when food is scarce (although sea-spiders do not appear to have much space for such storage) or larger foraging areas.
It may be that gigantism is linked to the species' evolutionary past as island biotas also show a mixture of dwarfism and gigantism related to the size of their mainland ancestors (e.g. Lomolino 2005). Could Colossendeis (or Bathynomus) be descendents of larger ancestors from warmer and/or shallower waters and thus display gigantism rather than dwarfism when adapted to polar/abyssal conditions?
Is their large size actually adaptive or is it simply a random evolutionary trait which happens to serve them as well as dwarfism might?
With many abyssal species tending towards dwarfism, might it provide a form of niche-separation and thus reduce competition?
Does large size itself reduce predation?
Might large size (through the ability to exploit a large food patch or larger food items) reduce the need to move and thus expend energy? Would this be a successful trade-off against the need for more energy/food to maintain a larger body size?
With the smaller surface area: volume ratio, larger bodies can mean easier temperature regulation, but would this be sufficiently adaptive and if so, why in only a few species?
With some hydrothermal vent and seep species such as vestimentiferan tubeworms showing great longevity (e.g. Fisher et al. 1997), and gigantism being at least partly associated with slow growth over a long period in a stable, if food-scarce environment, might gigantism be linked to an adaptive function of increased individual longevity in areas away from vents and seeps?

I suspect I could go on, but that is enough speculation for now. As always, comments and suggestions are most welcome - this is an area of ongoing research where the processes involved are, in part, poorly understood, so this may require an update at some point in the not-too-distant future. And the answer to the original question - polar or abyssal gigantism? Well, it seems likely that both are involved and linked to some extent by the influence of oxygen availability, but the relative 'weight' of each type of gigantism can not currently be determined for certain. However, my feeling is that, for Colossendeis at least, the fact that a single species can be found anywhere from the sea surface to depths of thousands of metres suggests that it is the polar aspect that is constant and having a greater effect. Could be wrong though!

Further reading

For a key to coastal British species: King, P.E. (1986). Sea Spiders. A revised key to the adults of littoral Pycnogonida in the British Isles. Field Studies 6(3): 493-516.

References

Arango, C.P. & Wheeler, W.C. (2007). Phylogeny of the sea spiders (Arthropoda, Pycnogonida) based on direct optimization of six loci and morphology. Cladistics 23: 255–293. Arnaud, F. & Bamber, R.N. (1987). The Biology of Pycnogonida. Advances in Marine Biology 24: 1-96.
Bamber, R.N. & El Nagar, A. (eds.) (2012). Pycnobase: World Pycnogonida Database. [accessed 09/02/2012]
Barnes, R.D. (1980). Invertebrate Zoology (4th ed.). Holt-Saunders, Philadelphia.
Chapelle, G., & Peck L.S. (1999). Polar gigantism dictated by oxygen availability. Nature 399: 114-115.
Fisher, C.R., Urcuyo, I.A., Simpkins, M.A. & Nix, E. (1997). Life in the slow lane: growth and longevity of cold-seep vestimentiferans. Marine Ecology 18(1): 83-94.Frazier, M. R., Woods, H. A. & Harrison, J. F. (2001). Interactive effects of rearing temperature and oxygen on the development of Drosophila melanogaster. Physiological and Biochemical Zoology 74: 641-650.
Kaariainen, J. & Bett, B. (2010). Evidence for benthic body size miniaturization in the deep sea. Journal of the Marine Biological Association of the UK. 86(6): 1339-1345.
Lomolino, M.V. (2005). Body size evolution in insular vertebrates: generality of the island rule. Journal of Biogeography 32(10): 1683-1699.
McClain, C.R & Rex, M.A. (2001). The relationship between dissolved oxygen concentration and maximum size in deep-sea turrid gastropods: an application of quantile regression. Marine Biology 139: 681-685.
McClain, C.R., Rex, M.A. & Jabbour, R. (2005). Deconstructing bathymetric body size patterns in deep-sea gastropods. Marine Ecology Progress Series 297: 181-187.
Peck, L.S. & Chapelle, G. (2003). Reduced oxygen at high altitude limits maximum size. Proceedings of the Royal Society of London B (Suppl.) 270: S166-167.
Pörtner, H.O., Peck, L.S. & Hirse, T. (2006). Hyperoxia alleviates thermal stress in the Antarctic bivalve, Laternula elliptica: evidence for oxygen limited thermal tolerance. Polar Biology 29: 688-693.

Timofeev, S.F. (2001). Bergmann's Principle and deep-water gigantism in marine crustaceans. Biology Bulletin 28(6): 646-650.

Van Voorhies, W.A. (1996). Bergmann size clines: a simple explanation for their occurrence in ectotherms. Evolution 50: 1259-1264.

Woods, H. A., Moran, A. L., Arango, C. P., Mullen, L. & Shields, C. (2008). Oxygen hypothesis of polar
gigantism not supported by performance of Antarctic pycnogonids in hypoxia. Proceedings of the Royal Society B 276: 1069-1075.
Wu, N. & Mastro, J. (2004). Under Antarctic Ice. University of California, Berkeley CA.

Birds in a box, beetles on pins

2012-02-08T14:58:00.002Z

For those involved directly in taxonomy and species identification, the function of biological collections is well known e.g. to provide reference specimens, and more recently to create a potential source of genetic material for molecular research. For others, it may seem a somewhat outdated, even macabre, activity, but this is not the case as long as ethical guidelines are followed - such as a 'code of conduct for collecting' (there may also be legislation covering collecting that varies from country to country, so do beware and check for protected species and permit requirements). During my recent visit to the Oxford University Museum of Natural History (which I've heard referred to rather dismissively as 'the dead animal building'), I came across two excellent examples of why biological collections are of key importance in life science research. The first is an area you may have noticed me writing about quite a lot - small beetles; the second is quite different but more widely familiar, at least in broad terms.

A tray of scarabaeid beetles from the Hope Entomological Collections at the OUMNH

Trays of insects on cards and/or pins is one popular perception of a biological collection, along with stuffed animals, skeletons and 'pickled things in jars'. Although this is no some extent rue (visually at least), their purpose is not always well understood. For example, one reason for my recent visit to the OUMNH was to consult the Hope Entomological Collections. With over 5 million specimens this is the second most important such collection in the UK after that at the Natural History Museum in London. My reason for wanting to consult the collection was to help finish my key to identifying British Chrysomelidae, in particular the last few tricky species of Longitarsus flea beetles - L. curtus, L. fowleri and L. membranaceus. These are superficially very similar and I wanted to check some characteristics so that I could decide how to separate them in my book. They are also tricky because (a) I don't have my own beetle collection (I have nowhere to store one), (b) there is a very good collection maintained by the Hampshire Museums Service in Winchester; however although it is only 10km away, it tends to only be open when I am at work (an increasing problem in the UK as local government funding cuts reduce staffing and thus opening hours), and (c) these three species are not available as clear online photographs, even at the excellent European Chrysomelidae website. So, I went to Oxford to have a look at theirs - in particular fine details of the heads.

Longitarsus membranaceus

Longitarsus curtus

Longitarsus fowleri

I won't go into great morphological detail here, but the result is that I can now tell these three species apart from details of their heads - and so will anyone else be able to once my key is published - but in summary, L. membranaceus has a distinctive broad bar running down the front of its head, the sides of the bar being more or less parallel where it runs between the upper halves of the eyes, and it has a narrow process extending down between the antennal bases. In L. curtus, there is a broad wedge rather than a bar and this meets the upper edges of the eyes. In L. fowleri, the bar broadens towards the top of the head but is still separate from the eyes. So, with specimens and a microscope, a fairly straightforward way to separate some very similar species without needing to dissect them - and one that does not appear in existing keys, but could not have been determined without access to a collection. Plus, as I remembered to take my camera, there are now some useful photos that will appear when these species are Googled! Now, moving on to the second example, I enter the realm of an iconic vertebrate, the dodo (Raphus cucullatus).

The Oxford dodo display

This was not something I specifically went to visit, though it is an important exhibit, not just because the dodo is a popular metaphor for extinction, but because of the the information that can be gained by having the specimen in a biological collection. It is well known that the dodo was first discovered by Europeans on Mauritius in 1598 and that it was extinct by 1680 (though probably due more to pressure from other introduced animals rather than hunting by humans - apparently it wasn't very tasty!). However, despite being so iconic, little was known about its biology and ecology until recently. The best-known contemporary images are 17th and 18th century paintings but their portrayals of fat dodos are now known to be inaccurate, with research since the 1990s indicating a much slimmer bird even if precise estimates differ and work is ongoing (Kitchener, 1993a, b; Angst et al., 2011). The importance of the OUMNH's dodo specimen lies in the fact that it is the only specimen in the world with soft tissue preserved (skin on the head) from which DNA could be extracted. When this was analysed, the dodo, and its close relative the solitaire Pezophaps solitaria from the (relatively) nearby Rodrigues island, were found to be most closely related to the pigeons within the family Columbidae (Shapiro et al., 2002). This is a key result as the dodo had previously been taxonomically linked not just to pigeons, but also parrots, shorebirds and raptors - partly due to the lack of evidence/specimens and partly because of the considerable amount of adaptation and specialisation that occurred in its island location that rendered it superficially unlike any other bird, apart from the similarly poorly understood solitaire. The research indicates that the dodo and solitaire separated from south-east Asian relatives around 40 mya while able to fly, and dispersed to the Mascarene Islands. The dodo and solitaire then separated around 26 mya; Mauritous and Rodrigues are much younger (only around 8 and 1.5 my old respectively) which implies that the birds used the now-sunken Mascarene island chain as stepping stones, with the isolation of Rodrigues implying that the solitaire was able to fly as recently as 1.5 mya.

So, although genetics is only one area of research, and like any other needs to be applied and interpreted appropriately, this is an example where a modern technique and a traditional biological collection were both required for research purposes and combined to produce important results - the dodo is much more than a stuffed bird in a case, and genetics needs real-world applications beyond 'bar-coding' of species. It also highlights the point that when a specimen is collected, its use may be unknown as this specimens dates from long before the concept of the gene had been thought of. For an overview of some other applications of this technology, Nicholls (2005) covers some important points, and for much more detail about the 'Oxford dodo', have a look at this excellent OUMNH factsheet which I mercilessly plundered for background information.

References

Angst, D., Buffetaut, E. & Abourachid, A. (2011). The end of the fat dodo? A new mass estimate for Raphus cucullatus. Naturwissenschaften 98(3): 233-236.

Kitchener, A.C. (1993a). On the external appearance of the Dodo Raphus cucullatus (L.). Archives of Natural History 20(2): 279-301.

Kitchener, A.C. (1993b). Justice at last for the Dodo. New Scientist. (28.8.93)

Nicholls, H. (2005). Ancient DNA Comes of Age. Public Library of Science Biology 3(2): e56

Shapiro, B., Sibthorpe, D., Rambaut,A., Austin, J., Wragg, G.M., Bininda-Emonds, O.R.P., Lee, P.L.M. & Cooper, A. (2002). Flight of the Dodo. Science 295: 1683.

Four of the best: spiny trilobites

2012-02-06T12:52:00.004Z

I visited the Oxford University Museum of Natural History a couple of days ago for the 9th Coleopterists' Day (more about that soon). While I was there, I had a wander round some of the exhibits and was distracted by a display of excellent trilobites. I have a couple of fossil trilobites at home, but nothing as spectacular as what was on show, so I felt compelled to take a few photos and find out a little more about them.

There are many good introductions to trilobites so I don't intend to spend long on this aspect, but to give alittle background, they are a group of marine arthropods that lived from the early Cambrian (about 526 mya) until the mass extinction at the end of the Permian (about 250 mya). They were incredibly successful and diverse with about 17,000 species currently known from the fossil record. Some scavenged, filter-fed or hunted on the sea bed while others swam and fed on plankton. Some, mainly in the family Olenidae, may have had a symbiotic relationship with sulphur-metabolising bacteria from which they derived nutrition (Fortey, 2000). Also, they grew as nymphs/instars through a series of moults, each becoming progressively larger, much like many modern-day invertebrates. Despite the rich fossil record, the taxonomy and phylogeny of trilobites remains somewhat uncertain - currently it seems plausible that they fit into the clade Mandibulata (i.e. Myriapoda, Crustacea & Hexapoda) (Scholtz & Edgecombe, 2005) although they have been popularly placed in the clade Arachnomorpha which includes all other arthropods. The jury remains out on which is correct (or at least the most appropriate).

However, rather than diving into evolutionary biology/cladistics which isn't my area, I would like to look at some examples from the OUMNH collection and highlight some of the (to me) unexpected aspects of their morphology and the possible functions of such structures. I will however give some links to factsheets which provide details of the characteristics placing these species/genera in their currently accepted orders. Firstly, the frankly bizarre Walliserops trifurcatus with its unmistakeable trident...

Walliserops trifurcatus showing the long trident at the front end.

This species is in the family Acastidae within the Order Phacopida (factsheet). I have written about a member of this order before as I have a good-quality fossil of Phacops sp., including some fine details such as eye structure, but nothing quite as impressively odd-looking as this. The genus is unusual in showing a departure from strict bilateral symmetry, particularly in W. hammii with its sideways-curled occipital spine. However, the most eye-catching feature is of course the trident. Its function is uncertain due to a lack of data (Chatterton et al., 2006), although the presence of horns strongly suggests sexual dimorphism rather than having a primarily sensory, protective or hydrodynamic function (Knell & Fortey, 2005), though one or more of these could have occurred secondarily. Instead it appears most likely that it was used in competition between males (much like the horns and antlers of certain modern-day male beetles) and/or as a feature involved in mate selection by females ("ooo, what a big getting-in-the-way-when-feeding trident you have"). More data may eventually tell, but I can certainly imagine the trident being used to flip rival males. A close relative in the same family is Comura bultyncki which is well armed with spines, including some which curve off-centre, but no trident.

A specimen of Comura bultyncki

Moving on to the family Styginidae within the order Corynexochida (factsheet), Kolihapeltis chlupaci is another spectacular spined species, this one being from a relatively rare genus characterised by long backward-curving spines which grow from behind the eyes and the back of the head. K. chlupaci also has a ribbed 'tail' (more technically the 'pygidium' formed of rear body segments and articulating with the rest of the body). The role of the pygidum in the addition of new segments during growth and development is discussed in some detail here, with large pygidia such as this having a protective function as a shield when the trilobite rolled up (like a modern woodlouse). Some styginids have spiny pygidia (Holloway, 1996) which again suggests a defensive function, although these spines are not present in K. chlupaci.

Specimen of Kolihapeltis chlupaci

Lastly I want to briefly look at the family Lichidae within the order Lichida (factsheet), in particular, the genus Ceratarges (the species was given in the museum but was obscured in my photo, so I only have the genus for certain though I think it is C. armatus). This is another genus with prominent and impressive spines and horns. Some, such as C. spinosus have secondary spines - short 'thorns' pointing out at right-angles from the main spines. These again are likely to have an defensive function and I have to wonder whether they have a role in mate selection and competition between males as suggested for the tridents in the genus Walliserops.

Specimen of Ceratarges sp.

That's enough about these splendid beasts (for now). Given the cost of good-quality fossils of spiny trilobites, I don't think any will be added to my curio shelves soon, but if you are shopping for such things, beware fakes and learn how to spot them!

References

Chatterton, B., Fortey, R., Brett, K., Gibb, S. & McKellar, R. (2006). Trilobites from the Lower to Middle Devonian Timrhanrhart Formation, Jbel Gara el Zquilma, southern Morocco. Palaeontographica Canadiana 25: 1-179.
Fortey, R. (2000). Olenid trilobites: The oldest known chemoautotrophic symbionts? Proceedings of the National Academy of Sciences 97(12): 6574-6578.
Holloway, D.J. (1996). New early Devonian styginid trilobites from Victoria, Australia, with revision of some spinose styginids. Journal of Paleontology 70(3): 428-438.
Knell, R.J. & Fortey, R.A. (2005). Trilobite spines and beetle horns: sexual selection in the Palaeozoic? Biology Letters 1: 196–199.
Scholtz, G. & Edgecombe, G.D. (2005). Heads, Hox and the phylogenetic position of trilobites. In: Koenemann, S. & Jenner, R.A. Crustacea and Arthropod Relationships. Crustacean Issues 16: 139–165. CRC Press, Boca Raton.

What's in the box? No.13 - new to Nottinghamshire

2012-01-31T17:47:00.003Z

The most recent coleopterous arrival by post came beautifully carded inside the lid of a screw-top plastic pot complete with a label detailing the location, collection date and name of the person recording it. It came from a reserve warden who had been in touch with me because they had identified the beetle as Longitarsus dorsalis, a species that did not appear to have been recorded before in the county in which they found it (Nottinghamshire) and wanted the identification confirmed (or otherwise).

The neatly set specimen of Longitarsus dorsalis as it arrived by post - carded inside the lid of a screw-top plastic pot.

Now onto identification. The beetle is about 2.5mm long (as ever, excluding appendages), with dark elytra bearing broad orangey side-stripes, a similarly orange pronotum and a dark head and appendages.

Dorsal view of L. dorsalis

Within the genus Longitarsus, this coloration is only known from L. dorsalis in Britain and the genus is easy to determine as the first tarsal segment is more than half the length of the tibia. So, it seems that the identification is straightforward to confirm, but it is worth looking more closely to see some other features associated with the species (some more details and further images can be found here).

Hind leg of L. dorsalis showing key features

In this photo, the long first tarsal segment is clear to see (red line) and the tibial spur (green line) is shorter than the maximum thickness of the tibia (sometimes this can be difficult to tell as the spur length may be very close to the max tibial width). The upper surface of the tibia is flat (too dark to tell here, but it is) and the outer edge of the tibia has a fringe of short flat bristles (red arrow).

Pronotum of L. dorsalis

The pronotum is orange, usually with at least a dark patch towards the front (clearly seen above). The pronotum also has a fine but distinct rim along the rear edge (also visible above) and sides. The pronotal punctures are fine and between them there is finer microsculpture. The elytral punctures are coarser than those on the pronotum and the elytra themselves have definite 'shoulders'.

Head of L. dorsalis

The head is also densely microsculptured and although this isn't visible in the photo above, you can see the coarse punctures along the edge of the eye.

Side view of L. dorsalis showing the epipleura narrowing towards the rear (red lines).

In side view, the epipleura (lower edges of the elytra) narrow towards the rear, especially behind the mid-point (approximately where the left-hand red 'I' is in the photo above). Lastly, I want to look at the aedeagus (below) which is often a useful diagnostic tool when identifying some trickier-to-separate beetles. Here, the tip unfortunately broke off during dissection (though it did have a small blunt point), but the sides clearly curve inwards and the shape matches the better specimen illustrated here. The parameres (lateral lobes) can be seen as the dark V-shaped structure near the bottom. Interestingly, the curved sides of the aedeagus, an important feature, are not clearly shown in the usually excellent (and expensive) work by Warchałowski (2003).

Aedeagus of L. dorsalis

This clearly indicates that the specimen is of L. dorsalis which is important as it is the first time it has been found in Nottinghamshire, and is nationally scarce in the UK (Notable B). It is mainly found on calcareous or sandy soils, is associated with ragworts (Senecio), and has become scarce due to the loss of its habitats (conversion of grassland to agriculture, infilling of quarries, habitat succession such as in once-open woodland rides and clearings, grassland 'improvement' through fertiliser application, herbicide use and woodland clearance). Open conditions with ragwort are required and conservation measures can be straightforward e.g. retaining some open areas in woodland through rotational cutting, or grazing is some other situations (Hyman, 1992). So, it's good to see this species in a previously unrecorded location, especially as several individuals were seen with just one sent to me for identification.

References

Hyman, P.S. (1992). A Review of the Scarce and Threatened Coleoptera of Great Britain. Part 1. JNCC, Peterborough.

Warchałowski, A. (2003). The Leaf-beetles (Chrysomelidae) of Europe and the Mediterranean Area. Natura Optima Dux Foundation, Warsaw.

Observations of Macleay's Spectres IV: moulting and leg regrowth

2012-01-30T16:37:00.001Z

Parts I-III of this series have looked at different life-cycle stages and sexes of the Macleay's Spectre stick insect Extatosoma tiaratum. In this 4th part however, I want to look at processes and structures relating to ecdysis (moulting) and the regrowth of lost legs.

In invertebrates such as stick insects there is an incomplete metamorphosis with a series of nymphs (instars) that gradually increase in size but are approximately the same overall form as the adult. During each instar, the next larger 'skin' is grown wrinkled inside the existing one - when ready, hormonal effects detach the skin layers from each other and the old one splits along predefined lines of weakness. The next instar can then emerge, leaving an empty skin or 'exuvium'. This contrasts with groups that show complete metamorphosis where the larva develops into a pupa before emerging as an adult (imago) with a very different appearance - the most well known example of this is probably the butterflies.

In E. tiaratum, the soon-to-moult nymph clings to foliage or twigs with its legs, and the old skin splits lengthways along the dorsal midline of the thorax starting at the back of the head. The insect then pulls its front half free and leans backwards through this split, hanging by its still attached abdomen - the whole process takes from 30 minutes to two hours (Brock, 2000).

Final instar female E. tiaratum moulting.

The abdomen is slowly freed using muscular contractions to pull away from the old skin. When nearly free, the insect grips a suitable object and hangs abdomen-down as the new skin hardens and the insect takes in air to expand itself and stretch out the previously wrinkled skin - thus its overall size increases. This arrangement means that in captivity a container needs to be at least three times as high as the length of the extended insect; if the height is insufficient, the soft abdomen may press onto the floor of the container and harden with an unwanted bend which presumably may cause problems with digestion/waste elimination and reproduction if too pronounced. Apparently it is possible to straighten out unwanted bends by using a glued-on matchstick as a splint (Brock, 2000), but I have no wish to try this!

The picture above shows that the rear left leg is very small - this is due to a leg being lost during a previous moult. This highlights the risks associated with moulting and in this case was due to the old and new skins not separating around this leg. Having watched the otherwise fully moulted insect attempting to remove the still-attched skin for some time, I was forced to intervene and the leg was removed. However the loss of one (or even two or three) legs does not unduly affect the insect (in the wild it is a useful way to escape predators who are left with just a single twitching leg). Lost legs do regrow to some extent with successive moults but as seen here are smaller, starting as a thin black stump after one moult. Interestingly, research on another stick insect species (Sipyloidea sipylus) indicates that regrowing legs reduces adult wing size and hence flight performance, showing that there is a trade-off between development of legs and wings due to limited total resources for appendage growth and that this may have affected the evolution of this group (Maginnis, 2006) which has lost and regained wings on a number of occasions throughout its evolutionary history.

Usually, the old skin is eaten as the first post-moult meal, but occasionally it is lost (e.g. if it falls from its point of attachment) and subsequently ignored. I have also seen larger specimens eating the shed skin of another recently moulted individual. However, when a skin remains uneaten it is a useful way of investigating the finer structure of these insects and the moulting process.

A whole moulted skin of a male E. tiaratum showing the long wing-buds. This is approximately 40mm long although the curled abdomen means the insect was around 60mm long prior to moulting.

One feature visible here and in the top photo is the series of thin white threads around the head. These are not antennae (which are brown and can be seen underneath the head); instead they are the air tubes that form the trachael or breathing system of the insect and run internally from small air holes or spiracles along the sides of the abdomen. These are attached to the abdomen at the spiracles and so when the insect moults these also have to be pulled free and thus are found inside-out and external rather than internal.

The dorsal split through which the insect emerged during moulting. The air tubes are clearly visible here including their points of attachment at the spiracles.

Lastly, it is important to remember that in insects the eyes (both compound and simple/ocelli) and structures such as mouthparts and antennae are covered by part of the exoskeleton and so are also involved in moulting. The photo below shows the moulted surfaces of both types of eye - the arrow indicates and ocellus while the circle surrounds a compound eye.

The moulted head of E. tiaratum showing the surfaces of both types of eye.

References

Brock, P.D. (2000). A Complete Guide to Breeding Stick and Leaf Insects. Kingdom, Havant.
Maginnis, T.L. (2006). Leg regeneration stunts wing growth and hinders flight performance in a stick insect (Sipyloidea sipylus). Proceedings. Biological sciences / The Royal Society 273(1595): 1811-1814.

Observations of Macleay's Spectres III: the girls

2012-01-26T16:31:00.005Z

Following sections covering eggs and early nymphal stages and mature males, the third part of this series on Extatosoma tiaratum, the Macleay's Spectre, looks at mature females.

Female E. tiaratum with front legs raised.

As late-instar nymphs and adults, females are structurally very different from males (sexual dimorphism). They are larger - up to 150mm long with males around 100mm, broader and much heavier - up to around 30g (a lot for an insect and females often drag the spiny underside of their abdomen along the surface they are walking on, sometimes producing a clear scraping noise as they move). Females also have many more spines and flanges, including a more pronounced 'head-dress' of short blunt spines. In fact, in E. tiaratum, the differences between males and females are so pronounced that they were originally described as separate species (Hadlington & Johnston, 1998)! Details of female genitalia are given by Heather (1965) and note that from a sample of seven specimens there were on average 151 ovarioles (tubes forming the paired ovaries) with an average of seven oocytes (immature egg cells) each. The bursa copulatrix (the sac-like organ where the spermatophore or 'sperm packet' is stored after copulation) bears around 20 blind tubules and there appears to be no distinct spermatheca (sac for sperm storage) or other sclerotised (hardened) part of the genitalia. This matches the observation (see Part II) that sperm transfer is by spermatophore.

Flanges and spines on the leg of a female.

The spine-covered abdomen of a large female.

Side view of a female's head showing the oval extension of the top with its 'head-dress' of short spines. Also note that the camouflage includes marking breaking up the shape of the eye.

The head of a large female showing small wart-like bumps as well as a clear view of the mouthparts.

Around the same time my males changed to a brick-red colour, my two large females developed a pinkish-lilac tinge as shown in the photo of the abdomen above. This may be an indication of sexual maturity or possibly gravidity (containing eggs). Also, following their final moult, the adult females became noticeably more aggressive, making for interesting cage-cleaning sessions... This aggression included general attempts at evading capture (fleeing or dropping out of reach; previously these had not occurred often) plus active attempts to use spines as weaponry (such as pinching with the inner edge of a bent leg, nut-cracker style), including against unwary males that strayed too close soon after an angry female was replaced in the cage. I have seen one male with what appears to be a small healing puncture wound (i.e. a hardened drop of what I imagine to be dark haemolymph) on the ventral side of the thorax though whether this was caused by female aggression or an accident with a bramble thorn I do not know.

A female nymph already showing spines and flanges.

Side view of a late-instar female nymph.

As this pair of photos shows, the female structure develops at a relatively early stage, essentially just getting larger with each moult. This contrasts to some extent with males which show a number of significant structural changes following their final moult.

A big girl perching on my wrist. She is mighty!

So, I started this series of posts with eggs, and can return to this topic as two days ago one of the large females began laying eggs. This is not a precise process in E. tiaratum as eggs are flicked up to a few feet (maybe a metre or so) by twictching the abdomen when the egg is laid (this also occurs with frass AKA insect faeces which takes the form of dry 3mm x 5mm oval pellets of plant material - in males, frass is long and thin, approx 1mm x 5mm). Fortunately as my insects are in cages, the eggs are easy to collect so I hope to have another generation relatively soon.

Tip of a mature female's abdomen showing an egg about to be laid. Note the dorsal spines on the abdomen - they are splayed outwards which may be an adaptation to accommodate a male during mating.

A female nymph doing her favourite thing - eating bramble leaves, nom nom nom.

It's busy during cage-cleaning time.

References

Hadlington, P & Johnston, J.A. (1998). An Introduction to Australian Insects (revised ed.). University of New South Wales, Sydney.
Heather, N.W. (1965). Studies on female genitalia of Queensland Phasmida. Australian Journal of Entomology 4(1): 33-38.

Observations of Macleay's Spectres II: the boys

2012-01-24T17:56:00.003Z

Having looked at the early stages (eggs and small nymphs) of my Macleay's Spectre stick insects (Extatosoma tiaratum), it's time to move on to looking at the older males. As they develop through a series of nymphal stages (instars), moulting and expanding in order to grow, they develop small spines and flanges, but most obviously a pair of wing buds. In their final (5th) instar, these are quite obvious and when they moult, emerging as an adult, these develop into full pleated wings with long 'coat-tail' covers.

An adult male showing its long wing covers.

An adult male opening its wings just as it is about to take flight.

Once they have dried their wings (much like butterflies and other winged insects do), the males are able to fly strongly, and in the wild do so in order to find food and females, or to evade predation. However, I found that initially they were not very active apart from showing increased aggression when handled. During their final moult they also develop longer, curved antennae and larger, more protruding eyes, presumably used to find females both by scent at a distance and then visually when nearer. The wings fold along radial pleats (a bit like a parasol) and have a spotty pattern, and the neck is long and flexible at the joint with the thorax.

Head-on shot of a male in a threat posture showing well developed eyes and antennae.

The males remain well camouflaged, moving in a similar manner to leaves in the wind. For a few weeks they retained their variable colouring - some males were greenish, others brown or greyish. However, after this time a change seemed to take place with most darkening to a reddish-brown colour, and becoming more willing to fly - most evenings, the vivaria are opened and some males readily walk onto my outstreched hand and then launch (this is preceded by a subtle but definitie raising of the body into a launch posture), often having climbed onto my head or shoulder first. Around the same time, the first males could be found mating with the large adult females (more about them in Part III). So, it appears - albeit anecdotally - that this change in colour signals sexual maturity. If so, this is interesting as it does not seem to be associated with increased aggression either towards me (if anything they seem less aggressive when handled and simply fly more readily, though they may simply have habituated to handling, and some definitely avoid handling if possible) or other males. A number of males can be seen clustered around a female on occasions, but I have witnessed to overt aggression, though I have to assume that there is some form of competition to mate - maybe I need to observe what they are doing at 3am...

A male showing a dark red-brown colour and the long neck. The bright dot on top of the head is one of the male's ocelli (simple eyes).

A yellow-brown late (5th?) instar male nymph with the long wing-buds just visible behind the right middle leg.

Another late-instar (again, 5th?) male nymph, this one pale green in colour, again with the wing-buds visible.

When mating (or preparing to do so), males lie lengthwise along the back of a female (in the usual legs-outstretched 'stick' position) and both have genitalia at the rear of the flexible abdomens which bend to fit. The function of the long male neck with flexible articulation then becomes evident; females often arch backwards when feeding or moving and this forces the male's head backwards - the flexible neck allows him to remain in position without damage.

Males using my wife as a climbing-frame/launchpad while their cage is being cleaned. Just prior to this photo being taken, one of the males appeared to be trying to mate with her hair-grip (it has strong legs and a handy, accommodating central groove...)

Sperm transfer takes place in the form of a spermatophore - a packet of sperm in a hard 'shell' which novice insect keepers sometimes mistake for eggs. The spermatophore of E. tiaratum was noted by Clark (1975) and has been well documented since, but it was not until relatively recently that review of research and observations (e.g. Bragg, 1991) concluded that this structure provided the usual method of sperm transfer in the order Phasmida (AKA Phasmatodea). I recently collected an E. tiaratum spermatophore from the floor of one of my containers at home. The photo below shows the outer structure - the thread attaches it to the male during transfer to the female and the sperm-containing sac is 2.5-3mm in diameter, the whole being white with a pink tinge especially where the thread attaches to the sac.

Spermatophore of E. tiaratum

That's all for the males, but why not check out Part III: the girls...

References

Bragg, P.E. (1991). Spermatophores in Phasmida. Entomologist 110(2): 76‑80.
Clark, J.T. (1975). A conspicuous spermatophore in the phasmid Extatosoma tiaratum Macleay. Entomologist's Monthly Magazine 110: 81-82

Observations of Macleay's Spectres I: early stages

2012-01-22T17:50:00.003Z

Last summer, I was given an unusual birthday present - a 35mm film canister full of eggs of the Macleay's Spectre stick-insect Extatosoma tiaratum, sometimes known as the Giant Prickly stick-insect. These are found mainly in the Australian forests of Queensland and New South Wales where they feed on the foliage of eucalyptus trees, although in captivity they eat a range of unrelated species - one popular food is bramble (Rubus fruticosus agg.) which is what I use as it is readily available for free. However, young bramble leaves can contain noxious chemicals that make them unpalatable or even toxic, especially to young insects - I tend to remove these, and when some have been included by accident with more palatable older leaves, the insects ignored them.There is plenty of information about this species (e.g. from the Phasmid Study Group) as they are popular pets for those who like their companion animals to be six-legged, but I have made some observations which may be of interest. So, let's start at the beginning - with eggs...

Egg of E. tiaratum with the lid (operculum) open.

Close-up of the operculum showing the translucent sealing membrane around the edge. There is another membrane below this which seals the opening to the egg and which is broken to allow emergence by the first-instar nymph.

The eggs are a few mm long, oval with a sculptured ridge along one long axis, and a round lid (operculum). They are speckled with various shades of yellow and brown, camouflaging them to look like seeds when they fall to the forest floor in the wild. In those I have at home, the eggs are a pale yellow-brown when freshly laid and dry, but when placed on damp tissue to (eventually) hatchm they become a dark brown - presumably this aids camouflage with dry soil conditions also being paler and darkening when there is rain. When females lay eggs, they often flick them several feet by twitching their abdomens, presumably to aid dispersal - the function of this might be to prevent a cluster all being eaten in one go by a predator. The eggs have a coating (made of lipids and other organic materials) which is edible to ants and which induces them to take the eggs to their colony and eat this coating. The eggs remain otherwise intact and the ants dump them on the colony's waste pile where they hatch. Thus the eggs are likely to become clustered following the initial dispersal during laying but will have spent much of their time in an ant colony where the chance of predation is much reduced. Luckily, the eggs can hatch without the attention of ants which means that those missed by foraging ants and of course those in captivity remain viable.

Unsurprisingly, given their birthplace, E. tiaratum hatchlings (forst-instar nymphs) are ant-mimics, specifically of the large, long-legged 'spider ants' in the genus Leptomyrmex.

Recently hatched nymph showing the orange head and black body providing its mimicry of Leptomyrmex ants.

The orange head and black body, as well as overall shape closely mimics that of ant species such as L. darlingtoni, L. erythrocephalus and L. rufipes and so benefit from appearing similar to these toxic species (the sting has degenerated in this group of ants and they instead secrete a chemical repellant).

When my specimens hatched, I couldn't help but notice that the nymphs were highly active (a well-known characteristic) and that their preferred direction was definitely up. This makes sense as they hatch on the ground but are foliage feeders and so need to climb quickly into trees to find food. After their first moult, they lose their ant-mimic coloration and develop one of a range of camouflage colours - oranges, yellows, browns, greys and greens - and they also become much less active, more like the typical behaviour of a stick-insect. They do make swaying movements to mimic the motion of leaves, especially when disturbed, but otherwise spend much of their time stationary or moving slowly as they feed, though being nocturnal much of their activity goes unobserved (or would if I wasn't so nosy). The image below shows three nymphs at different stages and with different colours. In subsequent parts of this series, I'll be looking at changes in colour and behaviour (in males and females, highlighting sexual dimorphism) plus the process of moulting.

Three nymphs showing different colours and stages of development. The two smaller ones are 2nd instar nymphs, the larger one a 3rd instar.

Teeny-tiny toadstools - or are they?

2012-01-16T12:37:00.001Z

Yesterday I was pointed towards a log cut from a fallen tree in my in-laws' garden. On it was a fairly dried-out growth of moss and on the leaves, what looked like some tiny (1mm) fungal caps. Now, I'm no mycologist (or bryologist), but I do find microfungi intriguing and happen to have a copy of Ellis & Ellis (1998) which is the standard (only?) work covering British microfungi on substrates other than vascular plants - for those you need Ellis & Ellis (1997).

The specimen - the caps are about 1mm in diameter.

A slightly closer view showing the wrinkled stalks.

The moss is fairly dry and a bit of a miserable specimen without capsules, but looking at the excellent Atherton et al. (2010), I think that it is the common and widespread species Brachythecium rutabulum (sometimes known as the Rough-stalked Feather-moss). The fungus itself is white with a split cup-like cap and a wrinkled stem that widens towards the base. The cap is granular beneath and bears hairs in the upper/outer surface.

Two of the fruiting bodies showing details of stems and caps.

Side view of a fruiting body showing the split cap and granular spore-bearing structures.

Some moss-epiphytic microfungi have clear fringes of hairs around the edge of the cap. This doesn't appear to be the case here - instead there appears to be an irregular tufting of hairs on the top of the cap with a few at the edge (I wondered if they were the hyphae of another even smaller fungus, but I don't think so).

Side view of the cap showing tufts of hairs.

High-power image of the cap showing branching hairs.

Lastly, spores are an important feature used in the identification of microfungi. I collected some of these on a slide and they are clearly almost spherical and reddish-brown in colour, and each is about 10um in diameter.

Spores (x100 magnification)

So, the overall size, colour, spore colour/shape/size, habitat, hairs and other features lead me to tentatively identify this as Chromocyphella muscicola, a species with caps up to about 3mm diameter which is associated with mosses on bark. However, having consulted with a mycologist from the Hampshire Fungus Recording Group, it appears that C. muscicola doesn't produce stalks like this. Other superficially similar genera such as Leptoglossum also differ from this specimen in one or more ways e.g. spore shape, cap hairs. And so, it was suggested that this might not be a true fungus at all, but instead a myxomycete or 'slime mould' where the globular sporangium had broken open to reveal the network of spore-bearing hairs known as the capillitium.

I have posted about myxomycetes before (e.g. here and here) but it still a group of organisms I know little about, fascinating as they are - taxonomically protozoans but traditionally treated as 'honorary' Fungi. So, swapping books to look at Ing (1999), it soon became clear that this was indeed a 'myxo'. It also happened to be one that was relatively easy to identify from the keys and descriptions - the pale colour, size, stalk, open split 'cap' with the hairs of the capillitium, and spores (shape, size, colour, texture). This process also taught me that an important identification feature can be the shapes, colours and sizes of nodes of the capillitium i.e. structures about the size of a spore where hairs meet and branch.

These features all combined to indicate that this is the myxomycete Physarum nutans - a common and widespread species, though rarely found on mosses (it is usually on dead wood or the bark of live trees). It is very similar in appearance to Didymium squamulosum but they can be separated by features such as the spores (in D. squamulosum they are dark brown in transmitted light whereas in P. nutans, as here, they are pale brown). So, an interesting process for me, looking at an unfamiliar group - the only way to learn more about species identification!

References

Atherton, I., Bosanquet, S. & Lawley, M. (eds.) (2010). Mosses and Liverworts of Britain and Ireland: A Field Guide. British Bryological Society.
Ellis, M.B. & Ellis, J.P. (1997). Microfungi on Land Plants: An Identification Handbook. Richmond, Slough.
Ellis, M.B. & Ellis, J.P. (1998). Microfungi on Miscellaneous Substrates: An Identification Handbook. Richmond, Slough.
Ing, B. (1999). The Myxomycetes of Britain and Ireland: An Identification Handbook. Richmond, Slough.

What's in the box? No.12 - when typical species ain't so typical

2012-01-13T17:29:00.000Z

Back to the small beetles today - I've just finished identifying all the specimens that I received by post a while back (yay!) - most were fairly common, though a few such as the chrysomelid Phyllotreta punctulata were scarcer (in Britain at least). However, 'common' does not necessarily equal 'easy to identify' and here are a couple of examples from the family Chrysomelidae (leaf-beetles). The first is a deep metallic blue beetle about 4mm in length (without appendages).

The first specimen, a shiny blue chrysomelid beetle about 4mm long.

One very clear feature here is the pronotum being considerably narrower than the elytra. The length of the pronotum is about 0.4 that of the elytra and the elytra are about 1.6-1.7 times as long as they are wide. The overall form is distinctive and indicates it is a member of the subfamily Criocerinae.

A close-up of the pronotum with key features indicated.

Looking more closely, the green arrow on the left points to a rounded but definite angle (i.e. the side if the prronotum is not evenly rounded) while the red bracket shows that the constriction near the rear of the pronotum lines up with the furrow across its upper surface. These features separate it from the genus Lema (which would have the constriction near the rear of the pronotum and not in line with the furrow, and would also have sharper angles on the side), and hence show it to be in the genus Oulema - there is a good page separating L. cyanella and O. obscura here which also covers some of their taxonomic confusion. In Britain there are three Oulema species which are this colour - obscura, septentrionis and erichsoni.

O. obscura (often known as O. gallaeciana in continental Europe) is generally considered to be a fairly short species with a pronotum 0.3 times as long as the elytra and with elytra 1.25 times as long as wide. So, using these features, it would appear to be one of the other two, more elongate, species. However, there is a problem here - O. septentrionis is found in Ireland, but not on the British mainland while O. erichsoni has, since the early 20th century been found only in Somerset (a county in the west of England). This specimen was collected in Essex (a county in the east of England) which means one or more of a few things - either it is one of the above two species well away from its usual area (this is unlikely), it is a species new to Britain (very unlikely), the key is not correct (possible - I'm using my own key which is not yet complete) or it is an unusual specimen of O. obscura (also possible).

So, I decided to start with the specimen and looked for some other images which might show some variation in length:width ratio. This turned out to be quite simple - some pages such as this one showed specimens of similar proportions, while Google Images provided many which were more elongate still (though of course these may not all be accurate identifications). So, I am certain that this is indeed O. obscura, though I will add a note to my key about the variation in proportions.

The second specimen is smaller (about 2.3mm without appendages) and less brightly coloured and is in the genus Aphthona - the leg shown below is twisted but the tiny tibial spur is on the outer side of the lower edge (if in the middle of the lower edge, it would be in the genus Phyllotreta).

The Aphthona specimen - a male with the aedeagus partly protruding.

In Britain, only three Aphthona species are this colour rather than being black/blackish - lutescens, pallida and nigriceps. Some fine details of the head, including its colour (not black - actually paler than shown here) strongly suggest that this is A. lutescens, however this species generally has a partly darkened elytral suture (i.e. where the wing cases meet) as shown here. This does not appear to be the case here, but a very close examination showed that the suture did have a hair-thin dark line and that the darker areas such as the femora and apical half of the antennae were starting to darken. Therefore, this appears to be a teneral specimen of A. lutescens i.e. one that has only recently emerged as an adult and has yet to fully develop its coloration. Teneral specimens can often prove problematic as normally distinctive features may be missing. However, I wanted to check to be absolutely certain, so I looked at the aedeagus which was helpfully protruding.

The aedeagus of the probable A. lutescens.

Looking in Warchalowski (2003), the aedeagus is shown to have a small construction near the end forming a tiny protuberance. This is present here and is not seen in A. nigriceps or A. pallida, hence A. lutescens is confirmed and provides a helpful reminder of the need to take care with teneral specimens.

So, with the current batch of specimens identified and returned to their collector, this phase of the 'What's in the box?' series has come to a conclusion, but more will no doubt appear, so watch this space!

References

Warchalowski, A. (2003). Chrysomelidae. The Leaf Beetles of Europe and the Mediterranean Area. Natura Optima Dux, Warsaw.

What's in the box? No.11 - get into the groove

2012-01-05T18:00:00.000Z

A few weeks ago I wrote about the use of pronotal grooves as identifying characters in some leaf beetles (Chrysomelidae). Continuing through the box of specimens I was ent for identification (I'm now about half way), I found this one, about 2mm long without appendages.

Another small brownish leaf beetle!

Even at this scale, it is easy to see that the end of the hind tibia has a wide curved dent on the outer edge. In close-up, the dent is quite obvious and a fringe of hairs on the upper edge can be seen.

Tibial dent with fringing hairs

This dent means that the beetle is in the genus Chaetocnema - it looks like the fringed dent could be used for cleaning another appendage but I must confess I don't know what its function is and I can't find it mentioned in any of the literature I have or via a fairly quick web-search; if anyone knows, please do post a comment here! Anyhow, moving onto species-level identification, the head needs to be looked at closely to see if there is a keel running across between the antennae. In this case there isn't, but there are several punctures above each eye which I've tried to photograph - it was tricky and the clearest image is here with a puncture indicated by the arrow.

Head of Chaetocnema showing one of the punctures above the eye.

These punctures are helpful as they mean it can only be C. concinna or C. picipes. There has been taxonomic confusion between these species in the past (Booth & Owen, 1997; Cox, 2007), but even without dissection there is a subtle difference in the antennae. In C. concinna, the last antennal segment is clearly asymmetrical, while in C. picipes it is more or less symmetrical (and relatively narrow). In this case, the segment is narrow and symmetrical and the specimen is C. picipes, a beetle with a scattered distribution in Britain, found on Polygonaceae and oraches (Atriplex) as an adult, although the larval feeding behaviour is unknown (a project for someone).

Antenna of C. picipes with the diagnostic last segment arrowed.

References

Booth, R.G. & Owen, J.A. (1997). Chaetocnema picipes Stephens (Chrysomelidae: Alticinae) in Britain. The Coleopterist 6: 85-89.
Cox, M.L. (2007). Atlas of Seed and Leaf Beetles of Britain and Ireland. Pisces, Newbury.

Mutate, mate, sporulate!

2012-01-02T15:51:00.000Z

Back in the mists of time when my blog had just been born, I wrote a piece about Entomophthora - a fungal genus that parasitises flies, changing their behaviour to aid its own spore dispersal before killing the host. On that occasion, I had found dung-flies (genus Scathophaga, probably S. stercoraria) attached to the top of grass stems - the usual location for flies infected by this fungus. However, a couple of days ago, while putting some post-Christmas stuff into the attic, I noticed something quite different - two flies in the typical Entomophthora posture (proboscis attched to the substrate, abdomen lifted, wings spread), but indoors, attached to a skylight frame.

Fly attached to skylight frame.

Even in this photo, you can see the reddish fungal mass spreading out from between the abdominal segments, the proboscis tightly stuck to the frame and some powdery white spores on the legs and abdomen. However, these features are clearer if we look more closely. It's also helpful to identify the fly - it's one of the house-flies (Muscidae), but to separate the genera, a key feature is the wing venation.

Fly wing - the red arrow points to the bend in the discal vein.

The bend in the discal vein mean this is either Orthellia or Musca, but at the fly is clearly not metallic green, it is Musca, in this case M. domestica, the common house-fly. I don't want to go into muscid identification in any more detail here, but if you are interested, a key work on British species is d'Assis Fonseca (1968) which is available second-hand or by inter-library loan. So, returning the fungus and its fly host...

Side view of the abdomen - note the white spores stuck to hairs near the rear.

The underside of the abdomen, again showing the fungal mass and white spores.

Close-up showing individual spores attached to hairs.

Outdoors, this would be the typical method of spore dispersal as the spores are actively released and blow away or attach to other nearby flies, especially if there is direct physical contact. However, being indoors there is no wind and the spores have simply attached to the flies' own bristles, although it is of course possible that other house-flies have been infected (window-frames are a coomon place to find infected flies though I have not previously noticed them). My previous post covers infection routes and methods to some extent, as well as a little on taxonomy, so here I want to look at the basic structure and life cycle of the fungus in a little more detail.

Microscope 'squash' preparation of the fungal mass (magnification x400)

Several structures can be seen here as indicated by the coloured arrows:

Green: these are the asexual spores (conidia, singular = conidium) covered in a gelatinous coating that allows them to stick to flies once released, and are then seen as white powder attached to hairs and bristles.
Red: these small round structures are the spores themselves without the gelatinous coating.
Blue: this is a coated spore attached to one of the elongate conidiophores, stalked structures which produce spores by mitosis.

In Entomophthora muscae (which is almost certainly the species of fungus seen here), once the host fly dies, the conidiophores emerge from between the abdominal segments (forming the fungal mass seen in the photos above), and produce primary spores. If, once released, they encounter a suitable host, the spores germinate quickly (within a few hours ), a germ tube penetrating the insect's cuticle. Once the tube reaches the heamocoel (fluid-filled cavity around the insect's organs), the cytoplasm grows through the tube and into the haemolymph (effectively the mixture of 'blood' and other fluids that fill the haemocoel). Fungal hyphae then grow into the nervous system (as well as the rest of the body) causing the change in behaviour that induces host flies that are near death to climb to high points and adopt the typical posture mentioned before. The fungus also digests the fly's gut causing death after around five to seven days. New conidiophores develop around three hours later and the cycle of infection continues. However, if there is no suitable host, spores may develop into smaller secondary conidiophores which produce secondary spores.

So, a jolly start to 2012 with a gut-eating parasitic fungus - I will undoubtedly return with some small shiny beetles soon, but until then, Happy New Year :)

Reference

d'Assis Fonseca, E.C.M. (1968). Muscidae. Royal Entomological Society Handbooks for the Identification of British Insects 10(4b): 1-119.

The Ecology Spot says 'Have a cool Yule'

2011-12-23T13:43:00.000Z

Just a quick pre-Christmas message to say I hope you have a great festive season and thanks to all my readers. 'The Spot' has a growing readership which is great and has recently celebrated its 1st birthday. So, whether you like the taxonomic morphology of small beetles, occasional forays into palaeontology, or fearsome garden predators - among other topics - I hope you've enjoyed them. I'm off now for a few days - back next week.

Hungry Christmas robin - bring out yer crumbs!

What's in the box? No.10 - a tricky customer

2011-12-18T15:19:00.000Z

My epic beetle identification marathon continues... in envelope number 3 (of 20+ containing chrysomelid 'flea beetle' specimens collected in the Uk during 2011), I found the following, about 3mm long and a dark metallic blue colour.

The latest beetle specimen in dorsal view.

One of the first things I noticed was the groove running along the rear edge of the pronotum.

The groove along the rear edge of the pronotum.

Many chrysomelids have a groove in this position, but it varies between genera - some are less even in depth than this one and can have short furrows running forward from the ends. Along with features such as colour and shape, this indicates that the specimen is in the genus Altica. This is always potentially difficult as reliable identification of Altica species requires dissection - in this case of a male in order to see the aedeagus (identification of females is detailed in Kangas & Rutanen, 1993). However, the curved sides make A. ericeti unlikely while the elytra are rounded at the rear but not bulbous/widened, so it is probably not A. brevicollis or A. lythri. Similarly, the lack of small dents at the tips of the elytra suggest it is not A. oleracea. This leaves three British species - A. helianthemi, palustris and carinthiaca. These do differ to some extent in terms of the fineness and depth of punctures, shininess/dullness of the top of the head, prominence of the elytral shoulders and so on, but these features are somewhat variable and comparative and so, dissection of males is, as noted above, the only way to make a definite species-level identification. Pins and forceps deployed, the aedeagus was removed.

Aedeagus (ventral view)

Aedeagus (dorsal view)

Aedeagus (lateral view)

Immediately it is clear that this is not A. helianthemi which has an aedeagus that is more clearly broadened towards the tip and S-shaped in lateral (side) view. However the aedeagi of A. palustris and A. carinthiaca are very similar and care needs to be taken. Both are more-or-less straight in lateral view, end in a small point, have transverse wrinkles and are the same overall shape. Fortunately for identification purposes, there are some small but diagnostic differences allowing them to be separated. Firstly, on the right-hand side in the lateral view above, there is a distinct dent about one third of the way down - something that, although not always this clear, is seen in A. carinthiaca but not in A. palustris. Also, although the ventral views are very similar, the arched structures near the tip in dorsal view match those of A. carinthiaca and this is indeed the species we have here.

This is an interesting find as it was only recognised as a British species in 2000 (Cox, 2000) and is found on meadow vetchling (Lathyrus pratensis) in a variety of habitats, mainly in the south and east of England, though there has been a recent (2011) record from further north in Cheshire. Since 2000, there have been numerous records of this species in the UK and, although the Cheshire record has not yet been included on the database, the distribution is shown by the NBN as follows:

Distribution map of Altica carinthiaca in Britain © National Biodiversity Network

The south-eastern distribution is clear (this specimen, from Oxfordshire, is within the usual British range) and although there is evidence of some expansion of range e.g. in Finland since the 1980s (Kangas & Rutanen, 1993), it is likely that this species has been present but overlooked in Britain for some time. Indeed, the difficulty of identification (given that even the aedeagi can be similar in some cases) has meant that it has been confused with both A. palustris and A. helianthemi, the latter when known as A. pusilla var. montana, with museum specimens at least as early as 1939 being attributable to A. carinthiaca (Cox, 2007).

So, we have a species which, although not a rarity, was overlooked until fairly recently, so records are valuable in order to provide information about its British distribution. It is also a good example of the importance of dissection in the identification of some chrysomelid species, especially the 'flea beetles' as well as showing that even once dissected out, care may be needed to accurately use sometimes subtle and variable features of structures such as the aedeagus. Now, where's that 4th envelope of beetles..?

References

Cox, M.L. (2000). Progress report on the Bruchidae/Chrysomelidae recording scheme. The Coleopterist 9(2): 65-74.

Cox, M.L. (2007). Atlas of the Seed and Leaf Beetles of Britain and Ireland. Pisces, Newbury.

Kangas, E. & Rutanen, I. (1993). Identification of the females of the Finnish species of Altica Müller (Coleoptera, Chrysomelidae). Entomologica Fennica 31(4): 115-129.

Egrets, I've had a few, but then again...

2011-12-16T12:07:00.001Z

OK, yes, the title is a terrible Piaf pun (je n'aigrette rien?) - maybe I'm feeling festive and frivolous... Anyhow, I've posted a lot of invertebrate taxonomic morphology lately, especially that of small beetles, so I thought I'd move up the size scale to look at a species that is probably one of Britain's most popular birds, the Little Egret (Egretta garzetta).

A little egret stalking through the water of a coastal scrape/lagoon

This is a small heron and its white plumage makes it both attractive and easily recognisable - the size and black beak separate it from other, scarcer, egrets in Britain. Although familiar to many people, its current British population size, around 1,600 wintering birds and 150 breeding pairs (RSPB, 2011) is a fairly recent phenomenon. Until the late 1980s, it was only seen occasionally, not breeding in Britain until 1996. This was a result of natural colonisation from France where, in previous decades, it had expanded from southern Europe into western and northern France following effective legal protection which allowed its population to recover after massive declines up to the 19th century as birds were killed to provide decorative hat-feathers. In fact, the decline of this species was one of the reason the RSPB was founded back in 1889. It is now seen regularly, especially along the south coast, and in East Anglia and Wales, but is included on the Amber List as a rare breeding species as the number of breeding pairs remains fairly small.

It feeds on fish and other small animals (insects, amphibians, reptiles, crustaceans) which it hunts mainly by stalking in shallow water, sometimes also running with raised wings or shuffling its feet to disturb small fish; at other times they may simply stand still and ambush their prey. While bird-watching yesterday, I was pleased to see a little egret using the foot-shuffling method (which the other British egrets do not use) and, although I'm no wildlife film-maker, I did manage to capture this footage (on a compact, hence the graininess, but the behaviour is still visible):

You can see the shuffling, sometimes circular foot movements which, at the end, result in the rapid (blink and you'll miss it) capture of a prey item. I hope you enjoyed reading this tale of conservation success - also a departure from the usual invertebrate theme - more coming soon.

Prey detected, the beak strikes!

Reference

RSPB (2011). Little egret. [accessed 16/12/2011]

What's in the box? No.9 - groovy beetles

2011-12-14T16:11:00.000Z

If you've been here before, you'll be used to my ongoing series about the identification of beetles that are sent to me my post. If, not here's a recent (and rather pretty) example to get you started. So, working through the recent numerous selection I received in an old Kodak slide box, I found a pair that summed up how the flea beetles (within the Chrysomelidae) are often perceived - small and sort of brownish...

A pair of flea beetles - even if you are new to this group, it's easy to see that the one on the left is male...

The presence of an exposed aedeagus (not usually seen without dissection) helpfully shows the difference in size between the male on the left (4mm long without appendages) and the female (5mm). The enlarged hind femurs are visible in dorsal view and show these to be 'flea beetles'. I won't go through the full identification process, but the combination of (1) hairless elytra (wing cases), (2) a strong unbroken groove at the rear of the pronotum (with foward-pointing ends), (3) bulges above the antennal bases being separated from the top of the head by a weak groove, (4) overall colour and (5) the top of the head without coarse/dense punctures show that it is in the genus Neocrepidodera.

Pronotum with a clear, broad groove along the rear edge with thin forward-pointing ends. The shallow, fairly sparse punctures and splayed edge can also be seen.

There are only three species within this genus in Britain. One, N. ferruginea, does not have the forward-pointing ends to the pronotal groove, which leaves us with N. impressa and N. transversa. Although very similar, N. impressa is found in coastal habitats such as saltmarshes and dunes unlike these specimens which were found inland. So, N. transversa is likely, but needs to be checked using the aedeagus - in this case easily visible.

Dorsal view of the aedeagus

Ventral view of the aedeagus

In this case, the identification is straightfoward - the tip of the aedeagus is spear-shaped, a characteristic of N. transversa, while in N. impressa it would be broadened and leaf-shaped (an example can be seen here, though note that the genus is given as Asiorestia as there is some taxonomic disagreement between British and continental authors). So, we have N. transversa, a widespread species found on a range of plants in various habitats (so, location may not help that much), but it is a nice easy example of the use of the aedeagus to separate closely related species. More small beetles coming soon...

I went on holiday and found an alien!

2011-12-12T15:08:00.001Z

Every now and again, me, my wife, and some friends go for a short holiday on the Isle of Wight (it's not far away and there's a house we can borrow for free!). Last time, we found a fossil crocodile - this time a small alien appeared inside on one of the windowsills...

Dorsal view of the insect which is 18mm long 'nose to tail'.

As it happens, it was already dead when found, but well preserved, just missing a front leg. This made it particularly obliging and easy to photograph. It's also a distinctive species in the UK and is an adult Western Conifer Seed Bug Leptoglossus occidentalis (note the white zigzag mark across the middle of the wings), a true bug (Hemiptera) in the family Coreidae (squashbugs). A native of North America, it was first found in Britain in 2007 when a single specimen appeared in a college in Dorset, southern England. Since then, there have been numerous sightings all over the country, though most commonly along the south coast, suggesting migration across the English Channel following its introduction to continental Europe (northern Italy) in 1999, after which it spread widely and rapidly. Nymphs have also been found in Britain, indicating at least one breeding population and adults have been known to enter buildings to hibernate (possibly the source of this specimen); adults fly well, making a buzzing sound - being relatively large (but harmless to humans), this means they are often easy to detect if they enter houses.

As the common name suggests, it is associated with conifers and feeds on the cones and seeds of over 40 species, particularly trees in the family Pinaceae. In North America, it can be a serious economic pest of conifer nurseries (e.g. causing a large proportion of conelets to abort) but in Europe it is generally found in gardens and parks so such impacts have not been seen, and future effects are uncertain - nor does it attack timber. So, let's have a look at our little alien in more detail.

Close-up of the head and pronotum (the 'head cone' is about 3mm long).

Here it is clear that the reddish pronotum has a detailed pattern of yellow blotches containing tiny black spots, while the head is dark with a central red stripe and other smaller red marks. Also, the antennae which appear smooth at a distance are actually densely covered in short bristles.

Dorsal view of the wings.

Here, the distinctive zigzag markings on the forewings are clearly visible, as is the venation of the membranous hindwings, the covering of short bristles, and the black-and-white markings on the edge of the abdomen ('connexivium').

Ventral view of the head and thorax showing the pointed mouthparts (rostrum).

The long rostrum is clearly visible here and is jointed with the section lying underneath the head having fine transverse lines (striations). The rostrum is formed from mouthparts modified to peirce and feed on plant tissues and is attached to the front of the head (in other suborders of Hemiptera, the attachment might be further back). You can also see where the front right leg was attached - now missing, there is a green blob where the point of attachment sealed over.

A close-up of the hind leg.

Lastly, the hind leg provides another distinctive feature (along with the reddish colour and pale zigzags) allowing this species to be easily identified. The inner edge of the hind femur is armed with sharp teeth, but the key feature is the flattened leaf-like shape of the hind tibia which can be seen clearly here along with the tiny black dots puncturing it. Again, although the legs look smooth at a distance, they actually have dense tufts of hairs.

So, although this species has only been in Britain for a few years, it appears to be spreading rapidly and as it is so distinctive, you have a fair chance of seeing one (possibly in your house), especially in the south. For more info on it, I recommend the excellent British Bugs page which includes links to a life stages chart and a more detailed factsheet (which provided some of the info here) as well as the recording scheme for sightings of this species in the UK.

Circus of the Spineless #68 - gifts galore!

2011-12-05T15:39:00.002Z

It's December, so it's tempting to come up with a festive theme for this edition of Circus of the Spineless. However, I'm going for a 'birthday' theme instead because it's my blog's 'official' 1st birthday - 'official' (like the Queen's) because it's about a year since it really got going though I started it a bit before that. And, my 20,000th pageview just appeared, so thanks to whoever that was! Anyhow, I digress - please do click to take a giftbox, a slice of virtual cake and/or a glass of whatever suits you...

First up, Susannah of Wanderin' Weeta fame has provided some gift-wrapped goodies found tucked away in a vacant lot ('brownfield site' in UK-speak!) which goes to show it's always worth a look. To celebrate, why not start with a slice of tasty cake...

Next, a pair of splendid parcels arrived from John at 'Carp Without Cars' - the first arrived as 'snail mail' but not really (you'll see what I mean, just drink from the glass of finest red) and the second comes in a smaller package that rarely displays its contents quite as clearly as this...

My birthday cup already runneth over, but there's more to come... Here, Daniel at 'Notes from Dreamworlds' takes a close, close look at some freshwater critters courtesy of some high-quality optics (feel free to contrast this with the microscopy efforts on my blog!) and wraps the whole thing up as an 8-minute video - a veritable treasure-chest of precious things.

And lastly, I shall give myself a small gift of shameless self-promotion... Here, I look at the shiny jewelled contents of a box that really did turn up in the mail, so why not sit back with an ice-cold beer - mmm.... foamy...

So, that's all from my birthday-themed CoS #68 - thanks for coming along to the party; the more the merrier and there's no-one on the door to check for invitations. Next month, prepare yourself for some myrmecology as CoS scuttles off to Wild About Ants. Byeeee.

What's in the box? No.8 - shiny shiny jewels

2011-12-04T17:06:00.000Z

In my previous article about beetles-by-post, I mentioned that I would soon get onto the reed beetles (family Chrysomelidae; subfamily Donaciinae) that I found in the first batch I looked at. Always one to keep my promises, here is the first one presented in all its bright and bejewelled glory...

The first of the two reed beetles; note the bright green elytra and pronotum and the long back legs.

This specimen is about 8mm long, not including appendages, and even at this magnification the rows of punctures on the elytra are obvious, as are the wrinkles on the pronotum. However, lets look at some closer detail - after all, the reed beetles look as if they should be easy to identify (they are brightly coloured and reasonably large), but species can in fact be quite difficult to separate as the colours are variable as are some other features such as spines on the legs.

A closer look - see the dents on the side of the pronotum and the pattern of wrinkles with a longitudinal marks down the middle. You can also see that the elytra are hairless.

A close-up of the head; this may not be needed for identification, but the fine detail is fascinating, including the sculpturing (a central groove matches the one on the pronotum), prominent eyes and tiny hairs.

Even closer still; looking at the fine detail of the elytra, you can see the punctures clearly and on the surfaces between them some fine 'microsculpturation' i.e. the surface looks shiny but isn't completely smooth.

Some of these features such as the pronotal wrinkles and the precise form of the central pronotal groove (e.g. whether it is complete or broken) are used in identification, but some essential features mean turning the beetle over.

Ventral (underside) view; the key structure here is the hind leg. Note the reddish colour at its base (the rest of the femur is dark) and the blunt tooth near the 'knee' joint with the tibia. The extent of red colour (if any) and the number/shape of hind tibial spines can be important features for identifying reed beetle species, not forgetting that some features (such as the spines) may vary between males and females - males have two femoral teeth, females have one as here although this is sometimes missing.

Zooming in on the hind tibia, a series of tiny teeth are visible on the ventral ridge.

This combination of features means this is a female Donacia versicolorea. This species is found distributed locally across Britain and is a good example of a variably coloured species - it can be darkly coloured or bronze. Adults are usually found in July and August, though this one was collected on 23rd June 2011, a little earlier than usual, though this year did have an early spring. The details above separate it from the similar D. crassipes which is larger (9-11mm) and has a pronotum that is microsculptured but not strongly wrinkled as here. D. dentata shares many features as well, but has dull elytra and two femoral teeth in both sexes.

If you are interested in British reed beetles, Menzies & Cox (1996) is excellent (and available as an unbound reprint for a few pounds) and will form the basis for the Donaciinae section of my forthcoming key to British chrysomelids. It also provides keys to separate the different genera (Donacia, Plateumaris, Macroplea), something I will cover in a subsequent article.

Reference

Menzies, I.S. & Cox, M.L. (1996). Notes on the natural history, distribution and identification of British reed beetles. British Journal of Entomology and Natural History 9: 137-162 + 2 pp. of colour plates.

What's in the box? No.7 - loadsa leaf-beetles and an interloper

2011-11-30T17:27:00.001Z

As promised, I'm back to my pet theme - beetles - in particular, the mysterious specimens that arrive by post because I coordinate the UK's Chrysomelid Recording Scheme which covers what are commonly known as leaf, reed, seed, tortoise & flea beetles (i.e. the Chrysomelidae, Bruchinae, Donaciinae, Zeugophorinae, Megalopodidae, Cassidinae and Orsodacnidae). So, now you are sufficiently overloaded with taxonomic terms (not to mention the fact that whether or not some are considered families or subfamilies varies by book/website), let's have a look at what prompted me to start writing...

What arrived in the post...

Usually I get a single specimen tube with one or two beetles in, but not this time... What I have here is an old Kodak slide-box full of about 20 little envelopes, each of which has several beetles of different species in. The envelopes are neatly labelled (date, location, UK grid reference) and the beetles look to be in pretty good condition. Also, the sender did get in touch first (and included return postage so he can have the specimens back once identified) so I expected more than the usual number of specimens. Most will be 'flea beetles' (subfamilies Galerucinae & Alticinae) as they are the ones the sender couldn't identify himself, and these are the ones most likely to be problematic (even to specialists on occasion). They also represent the parts of my test key which are receiving the most comprehensive rewrite as some of the keys to these genera didn't work well enough. So, although it will take a long time (it looks like there are about 100-200 beetles), it's really useful to have some unknown specimens to work through while I rewrite the relevant keys, as well as providing useful data for the recording scheme. It will also give me plenty to blog about... so, on to the first envelope!

A closer look at the contents of the first envelope.

Here it is clear that two of the beetles are larger (around 8mm long) and less smooth and shiny. These are reed beetles (subfamily Donaciinae) and will be the subject of a separate post soon. The one that stands out - to me anyway - is the small black roundish one more-or-less in the middle of the group.

A close-up of that round blackish beetle.

This beetle is around 3mm long and although shiny, you can see tiny punctures on the surface of the wing-cases (elytra). However, this isn't what grabbed my attention - it's the leg sticking out, in particular the pair of spurs at the joint of the femur and tibia. This gives me a good idea of what this beetle is, but let's turn it over to make sure.

Ventral view showing the enlarged hind femurs

Close-up of the enlarged hind femur. Personally I like the detail of small hairs in this photo.

The large femurs enable this beetle to jump and similar structures are seen in the 'flea beetles' within the family Chrysomelidae. However, flea beetles don't tend to be this round, nor do they have leg-spurs quite like those seen here; also, although you can't see the detail here, some fine details of the structure of the head are different from the chrysomelids. In fact, this isn't a chrysomelid at all - it is Scirtes hemisphaericus which is in the family Scirtidae and, as noted by Cooter & Barclay (2006), is sometimes confused with the flea beetles because of its legs and jumping ability. It's also in a family that is relatively unfamiliar, possibly because there is no modern book covering the British Scirtidae; however, the key in Joy (1932) still works well (although it was then called the Helodidae) and is available on a CD-ROM which is rather more affordable than the original 2-volume book (as it happens, I have the 1976 reprint which wasn't too expensive as collectors don't like ex-library books because of the stamps and marks - personally I don't care as long as it's complete).

I intend to continue this series, especially as I should have no shortage of material, interspersed with other ecological musings. In this case, I've started the 'mystery chrysomelid' thread with something that isn't a chrysomelid at all - I wonder what will appear next...

References

Cooter, J. & Barclay, M.V.L. (eds.) (2006). A Coleopterist's Handbook (4th ed.). Amateur Entomologists' Society, Orpington. An absolute must for beetle enthusiasts! Based on the UK beetle fauna.
Joy, N.H. (1932). A Practical Handbook of British Beetles (2 vols.) (1976 reprint). Classey, Farringdon.

What's in the box? No.6 - taxonomic confusion and big shoulders.

2011-11-22T14:53:00.000Z

OK, after my brief foray into palaeontology, it's time to get back to what I arguably know a bit more about - tiny invertebrates. You may have seen previous posts like this one and this one about the specimens that land on my doormat having been sent to me for identification as the organiser of the UK Chrysomelid Recording Scheme. I usually know that something is on its way as I ask for a little warning from contributors to make sure I don't get sack-loads of beetles when I'm busy, on holiday etc, especially as the organiser role is voluntary... This case was no exception as the collector had been in touch to ask about a specimen that appeared to be Aphthona ?atratula. Now, the ? in the name isn't a typo - it's there to indicate that there is some taxonomic confusion surrounding this species in Britain. Basically, A. atratula was referred to as A. atrovirens Foerster, 1849 by Pope (1977) but this species is not found in Britain (Cox, 2000). This means that British specimens of 'A. atrovirens' are probably A. atratula Allard, 1859. So, that's actually quite straightforward isn't it... well, actually, no. The problem is that various authors in continental Europe (e.g. Konstantinov, 1998) consider A. atratula to be the same as A. euphorbiae (Schrank, 1781), the Large Flax Flea Beetle. However, there are some quite convincing differences between British specimens of A. atratula and A. euphorbiae suggesting that they are actually separate - including the spread of A. euphorbiae with cultivated flax which is not seen in A. atratula (Cox, 2007). I happen to agree that they are separate species but officially this is not certain and so the ? remains. In any case, that's enough of the finer points of Chrysomelid taxonomy for now; let's have a look at the specimen itself.

Dorsal view of the Aphthona specimen, length 2mm excluding appendages. This is how it arrived in the post - very neatly (unlike my own card-mounting), glued onto a small card in a protective tube - thanks to Jon Cole for the good quality specimen!

First of all, it is an Aphthona - although I didn't get a clear photo of it, there is a spur on the outer side of the lower edge of the hind tibia (honest) - if it was in the middle of the lower edge, it would be in the genus Phyllotreta - see why the 'flea beetles' are considered so tricky to identify! I'm not going to go through the whole process of keying out Aphthona specimens here, but let's look at some of the final features required to make a species-level identification.

A close-up of the front half in dorsal view.

Looking at the pronotum, you can see some small 'punctures' - these are actually moderately coarse as finer ones would look more-or-less like a matt surface. So, it can't be A. melancholica which has very fine punctures - it is, as expected, either A. atratula or A. euphorbiae (remembering that Konstantinov, 1998 and several other important authors would stop at this point, considering the species to be the same). Both can be shiny black with a bluish reflection as seen here, however do have a look at the 'shoulders' of the elytra (wing cases). Here, they are well developed and are somewhat bulbous - this is characteristic of A. euphorbiae as is the size with A. atratula reaching no more than 1.7mm and having weakly developed shoulders. This is a fairly good indication that the specimen is actually of the common and widespread A. euphorbiae, but isn't strictly conclusive - to be really certain, dissection of the male genitalia is required (as is so often the case with small chrysomelids), and handily, this is a male.

Ventral view of the aedeagus.

Dorsal view of the aedeagus.

Side view of the aedeagus.

These images can be compared with those here at the excellent 'European Chrysomelidae' website. They clearly belong to A. euphorbiae - the dorsal view for example bears the same small polygonal structure at the base of the indent at the tip and the side view shows the same curvature. A. atrovirens (remember the taxonomic confusion...) however does not show the same small polygonal structure and the curvature differs slightly in that the inside edge of the curve straightens towards the tip.

So, we have a common species, but one that provides an opportunity to work through the taxonomy of Aphthona. Though often associated with cultivated flax/linseed (Linum usitatissimum) which they may kill by feeding on seedlings and cotyledons (Cox, 2007), it is actually found on many plant species in a wide range of habitats - as in this case where the beetle was collected (by beating in late October) from a Field Maple (Acer campestre) by a lake. Now, a box of about 20 little packets of beetles has arrived so I suspect this series will be updated soon...

References

Cox, M.L. (2000). Progress report on the Bruchidae/Chrysomelidae Recording Scheme. The Coleopterist 9: 65-74.
Cox, M.L. (2007). Atlas of the Seed and Leaf Beetles of Britain and Ireland. Pisces, Newbury.
Konstantinov, A.S. (1998). Revision of the Palaearctic Species of Aphthona Chevrolat and Cladistic Classification of the Aphthonini (Coleoptera: Chrysomelidae: Alticinae). Associated Publishers, Gainesville, FL.

The eyes have it: Trilobites as models of ecology and evolution

2011-11-21T16:57:00.000Z

Following my recent scribblings about cave bear dentition, I thought I would make the journey back to looking at extant invertebrates a step at a time. So, staying in the world of palaeonotology, but moving onto invertebrates (slightly more familiar ground), I decided to see if I could derive some more inspiration from my curio shelves. So, given that I've previously written about my Cretaceous water bug, it seemed about time I tackled that most popular of fossil invertebrates, the trilobite. Now, I've only got the one trilobite, but it's quite a good specimen, so here it is in all its glory:

My trilobite, 5cm long and showing clear segmentation plus its well preserved head on the right.

The shape of this, with a bulging and pimply glabella ('forehead') suggests it is in the genus Phacops (possibly P. rana) but not Reedops as this would have a smooth glabella. However, what brings me straight to the suborder Phacopina in the first place is its eyes (see Murray 1985 for a key to trilobite groups).

Phacops compound eye showing clearly separated lenses. This is the right eye looking from above and slightly off to the right. The pimply surface to the left is the fixed 'cheek' area known as the fixigena which appears as a lobe on either side of the glabella.

Trilobite eyes are compound like those of modern invertebrates (well, up to a point) but vary greatly, and this one is known technically as 'schizochroal'. Only found in the Phacopina, and not all of these, eyes of this type have relatively few relatively large lenses as can be seen in the photo. These lenses are well separated and if we took a section through the eye, apart from destroying my trilobite, we would see that each lens had its own cornea (outer layer - which we also have) and was separated from the others by a thick piece of exoskeleton called the sclera with the cornea extending down through this. This is not the case in most trilobites which have 'holochroal' eyes. These have small lenses which are often more numerous and may look more like our familiar 'mosaic' picture of an insect's eye. The lenses all touch each other (i.e. are not separated by sclera) and have a common cornea covering the whole surface of the eye. Lastly, a few trilobites (only the Cambrian Eodiscina) have 'abathochroal' eyes which have few, small lenses which are separated as in schizochroal forms but only have thin sclera and a cornea which stops at the surface of the sclera. Got all that? Well, I've only just worked through the anatony of these eye types and found an excellent summary on S.M. Gon's webpage 'The Trilobite Eye' which I recommend if you would like a expanded and illustrated version of my account here as well as other variant such as stalked eyes and those with inbuilt eyeshades!

Apart from my liking for all things morphological, one important aspect of these eye forms (and those trilobites that were eyeless) is what they can tell us about the life/ecology of trilobites. For example, eye loss is seen in some benthic (bottom-feeding) forms which lived in low-light conditions. So, starting with Phacops, it has fully developed eyes and can be seen as an ancestral form of genera with reduced eye development such as Cryphops which in turn evolved into the eyeless Trimerocephalus. So, we have a genus with well developed eyes which evolved into forms reducing and then losing them - a process that took a long time in human terms but occurred in the, er, blink of an eye, when looking at geological timescales (see Dawkins 1996 for more on the evolution of eyes of various types).

This loss of eyes in a benthic environment is a simple enough concept, but what about the development of schizochroal eyes in the first place? Unlike most (holochroal) trilobite eyes they are highly specialised and have no clear analogue in the modern fauna (Fortey, 2000). Firstly the lenses are crystalline, being made of calcite and are almost spherical, sometimes a little drop-shaped. These lenses have even had photographs taken through them and it is evident that sharp images could be formed and that larger 'pieces' of the trilobite's surroundings would have been visible per lens than for those with holochroal eyes. However, trying to use spherical transparent items such as marbles in a visual system doesn't work well because of 'spherical aberration' - the images become distorted, inverted, fuzzy. However, Phacops solved this problem by making the calcite impure, specifically by replacing some of the calcium atoms in calcite with magnesium and forming an internal 'bowl' in the lens which worked as a corrective structure, separating the eye into two sections of differing refractive index and allowing for the spherical aberration (Clarkson & Levi-Setti, 1975). So, although holochroal eyes would presumably have been good at detecting movement (food, predators?) as is the case in many modern invertebrates, Phacops could see chunks of detail. It is unknown exactly why this type of eye evolved, but it arose, like all other evolved structures, because it improved survival, in this case through a process known as post-displacement paedomorphosis (i.e. the retention of juvenile features - part-developed holochroal eyes are like smaller versions of schizochroal ones).

So, there we have it - Phacops evolved a visual system which has not (yet) been 'repeated', but why did I call trilobites 'models of ecology and evolution' in the title of this article? Well, the evolutionary side is well documented (despite what hordes of frankly bizarre creatonist and Intelligent Design websites might assert to the contrary - however, I won't go there...) both in the scientific literature and in popular-science publishing/broadcasting - despite the hundreds of millions of years that separate trilobites from our modern Earth, they are to some extent familiar. As for the ecology, it allows us to mix some evidence with a dash of speculation. Benthic lifestyles with low light levels led to the loss of eyes and so we can infer something of the 'lifestyles' of genera such as Trimerocephalus from their morphology as well as from the location and material in which they are found. However, in Phacops, we have some evidence of what level of detail they might have been able to see - I say might because their optic nerves are not preserved, thus their 'wiring' remains a mystery as far as I am aware, and by extension so is precisely how they perceived the world.

I'll stop there - I hope you enjoyed that, and please do watch this space for a return to the wonderful world of small beetles soon!

As in some modern invertebrates, the rear segments formed a section behind the thorax known as the 'pygidium' AKA 'the end'!

References

Clarkson, E. N. K. & Levi-Setti, R. (1975). Trilobite eyes and the optics of Des Cartes and Huygens. Nature 254: 663-667.
Dawkins, R. (1996). Climbing Mount Improbable. Viking, New York.
Fortey, R. (2000). Trilobite! Eyewitness to Evolution. Flamingo, London.
Gon, S.M. (2007). The Trilobite Eye. http://www.trilobites.info/eyes.htm [accessed 20/11/2011].
Murray, J.W. (ed.) (1985). Atlas of Invertebrate Macrofossils. Longman, London.

The Truth of the Tooth: Cave Bear dentition, ecology and extinction

2011-11-15T13:43:00.001Z

Lately I have written copiously about small invertebrates, particularly those found recently in our firewood store. So, having written five parts of the woodpile series (so far), I felt it was time for a brief departure - in terms of both time and scale as I have decided to look at some aspects of the Cave Bear Ursus spelaeus.

A Cave Bear skeleton in the typical (of museum displays) rearing posture.

Cave Bears lived in Pleistocene Europe (the Pleistocene epoch lasted from around 2.5 million to 11,700 years ago and covers the most recent series of repeated glaciations) and current evidence suggests they became extinct around 27,800 years ago. This means that they would have been encountered by humans and indeed they are depicted in cave art (albeit rarely e.g. at Les Combarelles cave in France). There is also possible evidence of Cave Bear worship by Neanderthals, such as at Drachenloch in Switzerland and Regourdou in France where the skulls of bears had clearly been arranged in and on man-made stone structures such as wall niches and a slab-covered pit. However, prehistoric anthropology, fascinating though it is, really isn't my area, so I'll stick with the more biological/ecological aspects. However, for an interesting overview of some aspects of human-Cave Bear interactions (focusing more on the earlier form of Cave Bear U. deningeri which disappeared around 100,000 years ago and may be an earlier species, a transitional subspecies or simply a pre-interglacial form of U. spelaeus), have a look at Stiner (1999). Taxonomic uncertainties aside, my interest was sparked when I bought a Cave Bear cheek tooth found in a cave in Romania, and dental evidence is where I will start.

Cave Bear cheek tooth, length 45mm.

This tooth is in pretty good condition (it's still shiny after about 40,000 years which shows just how tough tooth enamel is) and has an extensive grinding surface with a couple of large bluntly pointed cusps. Cave Bears lost their premolars as they evolved, a feature which has been used to suggest a highly herbivorous diet (e.g. Kurtén, 1976). The last premolar evolved as a molar (molarisation) which allowed tough plant material to be chewed more effectively (and hence more more food energy to be extracted) due to the increased number of cusps and cutting edges of the teeth, especially in the elongated last molar. Their teeth also show more wear than in most modern bears which again suggests a herbivorous diet with a large component of tough/fibrous materials, although detailed analysis indicates that tubers and other gritty foods were not a major part of their diet, unlike for modern Brown Bears U. arctos (Pinto Llona et al., 2005). However, varying threads of research in this area, including evidence for some cannibalistic scavenging (Pacher, 2000) has led to current scientific opinion tending towards Cave Bears being more herbivorous than modern bears of the genus Ursus, but still omnivorous to some extent. Recent re-examination of skull and tooth morphology (Figueirido et al., 2009) and analysis of the regional variation in bone isotope composition, especially nitrogen-15 (Richards et al., 2008; Trinkaus & Richards, 2008) both support this idea of omnivory and some variation in diet.

The same cheek tooth showing the pattern of the crown. The large grinding surface covers the left side of the tooth and the lower right side, with the pointed cusps to the upper right. The orange deposits in the grooves of the enamel are the remains of soil, although the right-hand end shows an area of worn (yellowish and not shiny) enamel at the base of the large cusp.

With advances in molecular biological techniques, the possibility of investigating cave bear genetics arose and in 2005, nuclear DNA extracted from a Cave Bear tooth around 42-44,000 years old was sequenced. This indicated that the Cave Bear was more closely related to the Brown Bear and Polar Bear U. maritimus than to the North American Black Bear U. americanus (Noonan et al., 2005) and supported earlier similar findings using mitochondrial DNA (Loreille et al., 2001). Interestingly, investigation of the fine structure of Cave Bear tooth enamel (the 'rods' or 'prisms' that form the basic units of enamel) shows that it retained carnivore-like characteristics despite the clear adaptation to a largely herbivorous diet. Thus, changes in broad dental anatomy driven by dietary specialisation can occur without the equivalent changes in enamel structure (von Koenigswald, 1992), meaning that Cave Bears had herbivore-shaped cheek teeth with carnivore-like enamel.

So, we have an extinct species of bear clearly adapted to a specialised herbivorous diet with some elements of omnivory and variation. As well as the genetic evidence mentioned above, its skeleton is similar to that of the modern Brown Bear, with the two species appearing to have diverged around 1.2 to 1.4 million years ago (Loreille et al., 2001) i.e. prior to the splitting of Brown and Polar Bears which may have occurred around 850,000 years ago, although this estimate is somewhat uncertain (Swenson, 2007). Males averaged 400–500 kg with females around half this weight at 225–250 kg (Christiansen, 1999), similar to the range for the largest modern bears, noting that they were larger during glaciations and smaller during interglacial periods (MacDonald, 1993), probably as an adaptation to adjust heat loss rate as larger animals have smaller surface area:volume ratios. The reason for its extinction is uncertain. It is unlikely to simply be due to its specialised diet and restricted geographical range ecologically 'marooning' it during post-glocial warming - after all, it had survived several similar changes in condition previously and there is possible genetic evidence of a decline starting some 25,000 years prior to its extinction (Stiller et al., 2010). Also, as noted above there is strong evidence for the species' ability to vary its diet. Instead, it is likely that there was a complex interplay of factors, possibly involving competition with humans for cave habitat, maybe specifically for hibernation sites as Cave Bears did not appear to use alternatives such as forest thickets and failure to find a hibernation site would lead to death. Despite numerous media reports taking the 2010 paper by Stiller et al. to be definitive evidence of competition with humans rather than changing climatic conditions to be the cause of Cave Bear extinction, there is still genuine scientific disagreement and research is ongoing. Further genetic work (Bon et al., 2011) does however show reduced genetic diversity from specimens in France originating from the period directly prior to extinction (genetic diversity is greater for specimens prior to this), again indicating a species under stress during human colonisation of the area - and the possibility of competition for hibernation caves.

References

Bon, C., Berthonaud, V., Fosse, P., Gély, B., Maksud, F., Vitalis, R., Philippe, M., van der Plicht, J. & Elalouf, J.-M. (2011). Low regional diversity of late cave bears mitochondrial DNA at the time of Chauvet Aurignacian paintings. Journal of Archaeological Science 38 (8): 1886-1895.
Christiansen, P. (1999). What size were Arctodus simus and Ursus spelaeus (Carnivora: Ursidae)? Annales Zoologici Fennici 36: 93–102.
Figueirido, B., Palmqvist, P. & Pérez-Claros, J.A. (2009). Ecomorphological correlates of craniodental variation in bears and paleobiological implications for extinct taxa: an approach based on geometric morphometrics. Journal of Zoology 277 (1): 70–80.

Kurtén, B. (1976). The Cave Bear Story. Life and Death of a Vanished Animal. Columbia University Press, New York.
Loreille, O., Orlando, L., Patou-Mathis, M., Philippe, M., Taberlet, P. & Hänni, C. (2001). Ancient DNA analysis reveals divergence of the cave bear, Ursus spelaeus, and brown bear, Ursus arctos, lineages. Current Biology 11 (3): 200–203.
MacDonald, D. (1993). The Velvet Claw: A Natural History of the Carnivores. BBC, London.

Noonan, J.P., Hofreiter, M., Smith, D., Priest, J.R., Rohland, N., Rabeder, G., Krause, J., Detter, J.C., Pääbo, S. & Rubin, E.M. (2005). Genomic Sequencing of Pleistocene Cave Bears. Science 309 (5734): 597–599.
Pacher, M. (2000). Taphonomische Untersuchungen der Höhlenbären-Fundstellen in der Schwabenreith-Höhle bei Lunz am See (Niederösterreich). Beiträge zur Paläontologie 25: 11–85.
Pinto Llona, A.C., Andrews, P. & Etxeberrıa, P. (2005). Taphonomy and Palaeoecology of Cave Bears from the Quaternary of Cantabrian Spain. Fondacion de Asturias/Du Pont Iberica/The Natural History Museum, Graﬁnsa, Oviedo.
Richards, M.P, Pacher, M., Stiller, M., Quilès, J., Hofreiter, M., Constantin, S., Zilhão, J. & Trinkaus, E. (2008). Isotopic evidence for omnivory among European cave bears: Late Pleistocene Ursus spelaeus from the Peştera cu Oase, Romania. Proceedings of the National Academy of Sciences of the United States of America 105 (2): 600–604.
Stiller, M., Baryshnikov, G., Bocherens, H., Grandal d'Anglade, A., Hilpert, B., Munzel, S.C., Pinhasi, R., Rabeder, G., Rosendahl, W., Trinkaus, E., Hofreiter, M. & Knapp, M. (2010). Withering Away – 25,000 Years of Genetic Decline Preceded Cave Bear Extinction. Molecular Biology and Evolution 27 (5): 975–978.

Stiner, M.C. (1999). Cave bear ecology and interactions with Pleistocene humans. Ursus 11: 41–58.
Swenson, J.E. (2007). Økologi hos en voksende bjørnebestand – Forvaltning når bjørnen har kommet tilbake. Det Skandinaviske Bjørneprosjektet [in Swedish] [accessed 15/11/2011].

Trinkaus, E. & Richards, M. P. (2008). Reply to Grandal and Fernández: Hibernation can also cause high δ15N values in cave bears. Proceedings of the National Academy of Sciences of the United States of America 105 (11): E15.
von Koenigswald, W. (1992). Tooth enamel of the cave bear (Ursus spelaeus) and the relationship between diet and enamel structures. Annales Zoologici Fennici 28: 217–227.

There's a Black Widow in my shed (not)!

2011-11-14T11:30:00.000Z

Recently, while writing one of my series about woodpile invertebrates, an Australian reader/blogger mentioned the rather larger and more dangerous invertebrates found down under - here in the UK, most invertebrates are harmless to humans and even those that can bite or sting rarely cause major problems unless you are allergic to them. So, when I found a particular spider in my shed, I was reminded of occasional media reports of people finding, or even being bitten by, 'black widows'. Now, we don't have black widows (genus Latrodectus) here, but we do have 'false black widows' (Steatoda) which are also in the family Theridiidae and look superficially similar. Spiders in this family are known collectively as the comb-footed spiders due to the bristles on the tips of their hind legs which they use to tease out silk to form 'tangle' - rather than sticky - webs.

My Steatoda specimen (about 9mm long) showing the bulbous abdomen typical of the Theridiidae - also note the short hairs. The pattern shows a pale, ywllowish arc and spots on a purplish background.

The features above show this to be S. grossa - a female - although the pattern can be highly variable or even absent; Roberts (1993) provides detailed diagrams of female epigynes and male palps if required for identification. This species is found mainly in and around houses in southern England (sometimes in coastal areas of the south-west) and although traditionally considered quite scarce, it appears to be increasing in range and frequency due to the warming effects of climate change. A similar increase has been seen in the non-native S. nobilis (NHM, 2007).

The Natural History Museum (NHM) receive enquiries about bites from Steatoda species, but spider-bites are uncommon in the UK (just a few reported each year); only 12 species are capable of biting humans (including the two Steatoda mentioned so far) out of a total of about 640 species. No-one has ever died of a spider-bite in the UK, and serious effects are rare (to be honest, true black widow bites are only occasionally fatal, though they are very painful and unpleasant). So, what should you do if you find a spider like Steatoda in the UK? Well, apart from temporarily incarcerating this specimen in order to take photos (it's now back in the shed along with other specimens, inlcuding males), I tend to leave them alone. If you want to handle them, it is easy to be careful by collecting them in a suitable container e.g. if you want to put them outdoors (or into the shed). Personally, I'm happy to leave them be, especially as I generally only see them when moving things around in the shed, at which point they flee and hide. Happy spidering!

Here's looking at you - a dorsal view of the pearly eyes of S. grossa.

References

Natural History Museum (2007). The truth about false widow spiders.[accessed 14/11/11]. Lots of snippets of info about this group of spiders in the UK.
Roberts, M.J. (1993). The Spiders of Great Britain and Ireland (compact ed.) (2 vols.). Harley, Colchester. This is the standard comprehensive work on spiders of the British Isles and is excellent, but it isn't cheap! There is a 2009 reprint by Apollo Books.

Bark at the Moon - small invertebrates of timber (Part 5)

2011-11-09T17:56:00.000Z

More from the smaller end of the macroinvertebrate scale... I got distracted from writing a book about some larger beetles (Chrysomelidae) and went back to the woodpile critters. Yesterday, I posted some images of the beetle Cryptolestes duplicatus and mentioned in passing that it was a parasite/predator of other beetle larvae. I didn't really elaborate on this at the time, so I decided to take another shot to get an image of the head and go from there.

The head of C. duplicatus showing the mandibles

As you can see, the mandibles are well developed as are the eyes so, despite being associated with bark (within a genus often associated with stored food products and thus seen as pests), it clearly isn't always in dark conditions - it may not be as fearsome as, say, a tiger beetle (Cicindelidae), but it appears well equipped to hunt. Although there is a lot of literature on Cryptolestes covering the pest status of constituent species and various taxonomic revisions, there doesn't appear to be much on its biology and ecology. However, Lukin (2010) does note that the larvae of C. duplicatus are fungus feeders beneath bark during the early stages of the decomposition of coarse dead wood.

Moving onto a species I haven't mentioned yet in this series, one other beetle caught my attention today, in particulaer the neat arrangement of hars on its dorsal surface...

Another small beetle - note the neat rows of long hairs and the curved ridges running parallel to the sides of the pronotum.

Similar in size to the previous species (around 1.7mm long), this was a relatively easy identification as I was familiar with its photograph in Hurka (2005), in particular, the pronotal ridges, long hairs and oval form. It is a specimen of Mycetaea subterranea and is in the family Endomychidae, close relatives of the ladybirds (Coccinellidae) - they are sometimes called the 'false ladybirds'. This particular species is sometimes known as the Hairy Cellar Beetle or the Handsome Fungus Beetle and is most often associated with cellars and outbuildings (barns, stables etc), although it is sometimes found in rotten wood inside hollow trees. Both larvae and adults feed on fungi.

That is enough for today - as mentioned before, I intend to keep working on the woodpile invertebrates and have some as-yet unidentified mites, barklice and, yes, beetles to work on, so this series isn't finished yet!

References

Hurka, K. (2005). Beetles of the Czech and Slovak Republics. Kabourek, Zlin.

Lukin, V. (2010). Species structure of the saproxylic beetles assemblages in the protected territories of Belarus.Muzeul Olteniei Craiova. Oltenia. Studii şi comunicări. Ştiinţele Naturii 26(2): 155-160.

Bark at the Moon - small invertebrates of timber (Part 4)

2011-11-08T16:47:00.003Z

After yesterday's brief journey off-topic (sometimes it just has to be done), I'm back to the tiny invertebrates found in our firewood store. As promised, I've started looking at the sub-2mm critters I must say are proving tricky. This is not because of their small size as such - after all, I have microscopes - but because they include taxa which are relatively unfamiliar, not only to me, but given the lack of literature covering some of them, to entomologists more broadly. There are also difficulties associated with handling them without damage (tiiiiny tweezers, small brushes) and storing them without some of the soft-bodied organisms shrivelling to almost nothing. This has as much to do with my lack of curatorial expertise with such species as anything else. However, there is an up-side; these issues probably mean there are some under-recorded species among the bark and dead-wood (saproxylic) invertebrate community and hence some interesting records if I can make species-level determinations. First up, another barklouse or 'psocid'.

A head-on view of a barklouse. The tiny size is highlighted by using the individual lenses (ommatidia) of the eyes as a rough idea of scale.

Although it can't be seen in the photo above (due to the specimen having shrivelled I think - it's still there but very faint), there is a diagnostic anchor-shaped mark on the 'face'. The wings are reduced to tiny buds and the abdomen has several rows of dots, still visible and appearing as round 'bumps' here, though their bumpiness is a bit of an optical illusion. This is the widespread Cerobasis guestfalica which has been spread internationally through commerce such as the timber trade. Almost all specimens found are females (males occur very very rarely) which means most poulations are entirely parthenogenetic i.e. they reproduce without fertilisation by a male (New, 2005). Moving back into my comfort zone - beetles - I managed to find a single specimen of a 1.6mm bark beetle.

Note the elongate shape, rounded antennal segments and longitudinal lines on the elytra and pronotum.

A close-up of the pronotum. The hind (left) angles have a tiny tooth and there are two slightly raised lines on each side of the pronotum - the inner one is quite clear, the outer one less so, though it can be seen as a broken bright line.

This beetle is in the family Laemophloeidae - not a group I am very familiar with - and to identify it, I needed to go back to Joy (1976). The features above did however allow identification as Cryptolestes duplicatus, a species which is probably predatory and/or parasitic on the larvae of other beetles. This species has a scattered, localised distribution in south and south-east England; not rare as such but not common either, and I suspect under-recorded (as well as having seen some significant taxonomic changes which have moved it from the genus Laemophloeus within the family Cucujidae), so quite a good find. Feeling bold, I thought I'd move onto something really small - a mite (so, an arachnid rather than an insect).

A mite showing the hard surface with a few long hairs (and some bits of plant material stuck to it!), but no velvety covering as seen in the more familiar 'spider mites'.

For now, I'm not going to try to identify this - I don't have much literature covering the mites, though I do think it is in the family Acaridae, based on its overall form. However, if I feel keen I might try later, in which case an update will appear here.

So, what next for the 'Bark at the Moon' series? Well, I still have some specimens to identify and I intend to continue collecting, so although posts in this series may slow down a bit, I strongly suspect there are more to come. After all, how else to investigate these under-recorded groups..?

References

Joy, N.H. (1976). A Practical Handbook of British Beetles (2 vols.). Classey, Faringdon. (This is the resized reprint of the original 1932 classic work). A CD-ROM is also available.
New, T.R. (2005). Psocids. Psocoptera (Booklice and Barklice). RES Handbooks for the Identification of British Insects 1(7): 1-146.

Why physics says convenience culture is bad for the environment

2011-11-07T17:12:00.000Z

I imagine some regular readers will have seen the title of this post and thought, "what?", "that's not what the Ecology Spot is about - what's Dave up to?" Well, I agree it is a bit of a departure from the norm - I generally keep away from the big science-and-philosophy topics because there are plenty of bloggers out there already doing just this, and in many cases doing it very well. However, an idea popped into my head and sometimes such ideas just have to be followed to see where they go... So, where did it come from?

Well, when I'm not scrutinising invertebrates and other organisms, I sometimes like to leave my comfort zone and delve into a bit of maths and physics - usually somewhere in between the paperbacks-for-beginners (too basic) and textbooks (too hard). To be honest, this is a fairly narrow line for a writer to tread, so there aren't that many books to choose from, but there are some - Feynman, Greene, Hawking, Penrose... ah, Penrose... You see, I've been reading his new book, Cycles of Time and very interesting it is too. Most of it isn't relevant here, but I got to one section (pages 77-79 in the 2011 paperback) which explained that the energy the Earth receives from the sun more-or-less equals the energy it radiates. I knew this (amaong other things, I teach courses covering climate change, so ought to really), and I knew that the 'yellow' photons from the sun have a higher frequency that the infra-red ones the Earth emits. What I had not realised was that this means that the sun provides the Earth with energy in a lower-entropy form than that which it emits. Que? Well, the overall amount of energy emitted equals that received but as this energy is spread across a greater number of lower-frequency photons, the entropy ('randomness') increases upon emission - there are more photons, hence more 'degrees of freedom'.

Now, you might quite rightly be wondering where all this is going and what it has to do with convenience culture. The answer is 'nothing' directly, but it is what started me thinking (always a risk) about topics like conservation of energy and so on. Without going into exactly how I got there, the key thought that appeared from all this was essentially:

"If 'convenience' means doing things without putting any personal effort in, where does the energy to do them come from?"

See what I mean? If I want to dig a hole in my garden, some resources are used to manufacture my shovel and provide me with food as fuel for my labours. However, if I decide that I want the hole without the labour, any other option (apart from not creating the hole) uses more resources. If I get a machine, this will have been manufactured using more resources than the shovel, and will need fuel (I will need to eat either way). An operator or delivery person may need to be paid and this money comes from my income which in turn, somewhere along the line, derives from the use of natural resources from a finite system. So, the more I spend (i.e. consume), the more resources are being depleted somewhere (unless all resources are fully renewable, which they aren't). Given how our economy works (or is meant to - it seems to be wobbling rather a lot at the moment), this ultimately derives from an environmental good of some sort - timber, oil or whatever - the impacts of which (deforestation, climate change, other pollution) tend to be treated as 'externalities' in economics i.e. they are not included as intrinsic costs. If they were, cheap disposable items would be a lot more expensive. The same goes for 'convenience' food and anything else which replaces our physical effort with work done by a device or process.

Now, I'm sure I'm not the first to notice this and I already know that extra packaging and energy use are involved in consumer goods (let alone the uselessness of many such goods in the first place) and more so if they are disposable, but it is the first time I've really thought about the fundamental physical inevitability of 'convenience' - we get nothing for free and if we don't do the work ourselves (whatever it may be), finite resources elsewhere have to do it for us, with the resulting impacts that entails. Of course, the above is greatly simplified - there are variations according to where my food comes from, machine efficiency and so on, and those involved in calculating carbon footprints, life-cycle analyses and so on will be familiar with such details. However, precise figures aside, 'convenience' = extra resource use.

OK, enough from me - I hope I stopped before descending into soapboxing waffle. Now those thoughts are out in the open, I shall be returning to the usual ecology next post...

Reference

Penrose, R. (2010). Cycles of Time. Vintage, London.

Bark at the Moon - small invertebrates of timber (Part 3)

2011-11-04T18:00:00.000Z

OK, only an hour to go before I head off to the firework display at our local pub, so apologies for any typos that get missed in the hurry...

Anyhow, as promised I've started looking at some of the tinier invertebrates found in our firewood store - by tinier I mean below 2mm but still visible (just) with the naked eye. I have quite a few still to look at, but the first is a springtail (Collembola) which despite its small size can be identified without a microscope if you have good close-up vision.

A springtail - the head is to the right and the 'spring' is out of frame to the left.

This springtail is Entomobrya albocincta and can be identified by the 'mane' of straggly hairs which also run along the dorsal surface, and the alternating dark and pale patches which give it a striped appearance. Even without a microscope, the palest mark just behind the head is clearly visible and the other mark just behind the mid-point can also be seen. This is a common and widespread species (there were plenty in our wood store) and is indeed usually associated with dead wood or found under bark (Hopkin, 2007).

As I mentioned above, I've only just started looking at the smaller residents of our wood store and I'm sure there are other sub-2mm specimens I'll be able to identify. However, along the way I found a couple of other interesting species, a little larger at 3-4mm.

An unusual creature - very flat with short wing-buds. Also note the pattern of red spots near the rear end. The overall colour and pattern provide excellent camouflage on bark and among lichen and plant material.

The 2nd and 3rd antennal segments are the same length. Note also the spines either side of the rostrum and the red eyes.

A close-up of the midline of the dorsal surface showing tiny pinkish tubercles (bumps) and other sculpturing.

This slightly odd-looking specimen is a nymph of one of the flatbugs, Aradus depressus, a true bug (Hemiptera) in the familt Aradidae. Adults develop fully sized wings and this species is often found on the damp ends of cut timber - no great surprise to find it among firewood. It is again a fairly common species and feeds on the mycelia (threads) and fruiting bodies of Polyporus and other fungi (Southwood & Leston, 1959).Moving on, I found what looked like another barklouse (psocid)...

A barklouse with short, hairy/scaly wings and long antennae. The bulging eyes suggest it is a male.

A close-up of the head - note the clear pattern of dark marks. The dense layer of silky hair-like flattened scales can be seen covering the wings and there are also larger bristles around the outer edge. The antennae have numerous small segments, each with its own small hairs.

This combination of features is quite distinctive and shows this to be a specimen of Pteroxanium kelloggi. It is usually found in leaf litter and is only rarely seen on bark or attached foliage (New, 2005), so is not usually associated with timber piles. It is the only species of the family Lepidopsocidae regularly found outdoors in Britain - there are three other species of this family known from Britain, but they are rare, casual introductions. The name of the family is also a good indicator of its form in this case - like the Lepidoptera (scaly-wings) i.e. the butterflies and moths, it is named after the dense flat scales on the forewings.

And so, we have some more species from our wood pile - it is turning out to be a local biodiversity hot-spot! It's time for the weekend to start now, but I should return soon with Part 4 of this series and hopefully more on the tinier residents.

References

Hopkin, S.P. (2007). A Key to the Collembola (Springtails) of Britain and Ireland. FSC, Shrewsbury.

New, T.R. (2005). Psocids. Psocoptera (Booklice and Barklice). RES Handbooks for the Identification of British Insects 1(7): 1-146.
Southwood, T.R.E. & Leston, D. (1959). Land & Water Bugs of the British Isles. Warne, London.

Bark at the Moon - small invertebrates of timber (Part 2)

2011-11-01T11:20:00.001Z

After yesterday's look at a species of barklouse (Psocoptera) which hasn't been known from Britain for very long, I thought I'd move on to the invertebrate group arguably most often associated with dead wood - beetles.I have so far only worked on the 'larger' (2-3mm) specimens that I collected late last week from our firewood store; tinier species remain to be identified...So, I shall begin with a broadly familiar group, the weevils (Curculionidae).

Side view showing punctures, cylindrical shape and broad, blunt rostrum.

Head showing rostrum (without a strongly broadened end or sharp basal excision) and bluntly pointed (rather than rounded) ends to the antennae.

Rear of elytra (wing cases) showing a flange round the edge (technically, formed by outgrowth of the 9th interstice or 'gap between rows of punctures').

Using the excellent work my Morris (2002) for this often fiddly group, these features lead to identification as Euophryum confine, a now-common species in Britain; introduced here from New Zealand in 1937, it has spread rapidly and can be a pest of timber (including buildings). I'll be checking our firewood carefully before bringing it indoors!

Next, a beetle with a broadly similar size and overall form (unsurprising for wood-borers that have to fit into tunnels and small holes) - despite only being 2-3mm long, this one was quite strikingly red in colour even to the naked eye.

Dorsal view showing reddish colour and cylindrical shape.

Ventral view of the head and thorax. The spines at the front corners of the pronotum are clearly visible, as are its smooth (rather than toothed) sides. Also, the 'temples' of the head are not sharply toothed.

Dorsal view showing that the pronotum does not have a pair of longitudinal grooves.

Again, this combination of features shows it to be a specimen of Silvanus unidentatus with Hurka (2005) proving useful for separating it from the rarer S. bidentatus. This is another cosmopolitan species which can be a timber pest. However, where there are small invertebrates, there are of course others for whom they are a food source. Some insectivores are well-known - many birds feed on small insects, and some of course break into wood to find them. However, among the small invertebrates of timber, there are similarly sized predators, in this case one of the true bugs (Hemiptera).

A bug with one of the fairly typical hemipteran body shapes, more or less droplet shaped with a pointed head widening evenly to the abdomen. This specimen is short-winged ('brachypterous') and the legs are yellowish with darkened femora.

Looking more closely, the wings are clearly brownish. Note the typical hemipteran scutellum - the triangular area between the wings and the pronotum.

This time using an older publication, Southwood & Leston (1959), it was fairly straightforward to key this specimen as Xylocoris cursitans, a bug in the family Cimicidae, the group which includes the bed-bugs (which have a similar general form to this species). A widespread species in Britain, it lives under the bark of fallen trees and is predatory on small beetles, springtails and thrips, and so may well help to control potential timber pests such as those described above. Of course, being a bug-nerd, I find the 'pest' species interesting in their own right, but I still have no intention of inviting them in to eat our tasty floorboards!

So, with the larger (relatively speaking) specimens covered, the next stage of my timber investigations will be to look at some of the tinier inhabitants to see what else lurks among the bark and wood-fibres. Part 3 hopefully on its way soon...

Part of our firewood store - it has since expanded considerably - what else will be calling it 'home'?

References

Hurka, K. (2005). Beetles of the Czech and Slovak Republics. Kabourek, Zlin. An excellent and well-illustrated overview of beetles from this part of Europe; the majority of species covered are found in Britain.
Morris, M.G. (2002). True Weevils (Part I). Coleoptera: Curculionidae (Subfamilies Raymondionyminae to Smicronychinae). Handbooks for the Identification of British Insects 5(17b): 1-149. Currently the standard work for this group in Britain.
Southwood, T.R.E. & Leston, D. (1959). Land & Water Bugs of the British Isles. Warne, London. Though old, this is still very useful and is available as a 2005 reprint (and possibly CD-ROM) from Pisces Publications, which is the version I have - the original is not cheap!

Bark at the Moon - small invertebrates of timber (Part 1)

2011-10-31T17:21:00.001Z

OK, it's Halloween and I seriously thought about posting something truly ghoulish, but in the end only came up with a slightly cheesy title... mainly because I spent part of the day identifying some small (2-3mm) specimens that I collected from our firewood store. There were some smaller specimens but I have yet to work through them (they may appear here soon); however, I thought it might be interesting to have a look at some of the invertebrates associated with stored timber, especially as they can be brought to our homes by hiding under bark and in crevices when forewood is brought in from elsewhere. Our firewood is all fairly local, so there is unlikely to be abything exotic, but given their small size, it is possible than some of the organisms found might represent under-recorded taxa.

The first of these is a barklouse which as its name suggests is associated with bark. These were numerous and as far as I can tell all those I collected were female and at least some were gravid (contained eggs).

Side view of the barklouse.

Dorsal view of the head showing features including the yellow patches at the inner rear edges of the eyes.

The 'laciniae', end segments of the maxillae (mouthparts) which have a distinctive shape (a 'pie-crust' edge) and are hardened for curtting and manipulating food.

The forewing showing hairs, vein/cell pattern and pale larks on an otherwise brownish wing (the other colours are interference patterns and reflections).

These features combine to provide an identification as Epicaecilius pilipennis. This species was first recorded in Britain in the late 1990s but has since been shown to be widespread (whether or not it is common) with specimens from Scotland to the south coast and various locations in between. It is in the family Caeciliusidae within which it is unusual in being associated with tree trunks rather than foliage (New, 2005).

It certainly seems locally abundant, but this is a species with a British distribution which is not well understood. This shows the value of looking in places such as household timber stores and sheds where overlooked taxa may well be found. More about our firewood inhabitants soon...

Reference

New, T.R. (2005). Psocids. Psocoptera (Booklice and Barklice). RES Handbooks for the Identification of British Insects 1(7): 1-146.

Rollin' rollin rollin' - the diverse inhabitants of a willow leaf

2011-10-27T15:35:00.000+01:00

Over the last year or so (yup, the 'Ecology Spot' is nearing its first birthday!) I've posting several musings on the inhabitants of galls - not only the gall causers but also other species that can make galls their home. However, there is something conceptually similar, and closely related biologically, that I haven't looked at yet, and that is leaf-rollers.

Leaf-rollers, as the term suggests, are organisms that roll leaves to form shelters - unlike galls, the plant doesn't grow new structures, although there is some overlap (excuse the pun) with some leaf-rolls including further distortions such as thickening and increases in cell number, and hence being considered galls (Redfern & Shirley, 2011). In this case, the roll in a willow (Salix) leaf (found at Winnall Moors on the edge of Winchester, southern England) involves twisting and thickening of the plant tissues and so is classed as a gall (only just - sometimes the thickening is very slight).

Willow leaf roll showing twisting and thickening (increased cell size is visible in places)

The downwards roll affects both sides of the leaf and most of the blade which indicates that it was caused by one of the Phyllocolpa species, a genus of sawflies in the family Tenthredinidae. Indeed, there were small dark sawflies with yellowish legs in the area which may well have been Phyllocolpa, although I did not manage to catch a specimen (either physically or photographically). As the larvae of these sawflies drop to the ground to pupate in the soil, it is not uncommon for galls to be empty, but the only way to find out is to look...

The roll unrolled - at first glance there is nothing but frass (invertebrate faeces)

Looking more closely, a few pale creamy-white rounded-oval eggs can be seen, each no more than 0.5mm in diameter. Whatever they are, an adult invertebrate was here recently. We'll return to these later...

A small cocoon of tangled silk. The lid (top right) is detached showing that whatever developed here has now left.

The bottom of the cocoon showing attachment threads plus a dark patch that may be frass.

So, we have eggs and an empty cocoon - is there anything more immediately identifiable? Well, fortunately yes. Whether or not they are in any way related to the cocoon I don't know, but two exuviae ('skins') were also present.

An unidentified exuvium - probably one of the Hemiptera (true bugs) with clearly defined wing buds and abdominal segments.

That's more like it - something recognisable, an exuvium of a small spider; even the leg hairs are clearly visible.

Although the 'bug' had long gone, the spider (or at least a spider) remained.

Dorsal view of the tiny spider (a few mm long) found in the leaf roll.

A close-up showing various appendages and some of the eyes.

Although the abdominal pattern seems quite clear, this is probably a juvenile. From the general form, I suspect it is one of the orb-weavers (Araneidae) though I would be more than happy if an arachnologist could clarify! If it is this family, it may be using the leaf roll for shelter as hunting takes place on an orb-web (a small one may have been present but un-noticed of course). Along with the spider I also found the following insect already dead (the abdomen was dry and wrinkled) - I wonder if it had become spider-food?

Ventral view of the insect showing the pointed 'snout', long antennae and spotted wings held in a tent-like position.

Dorsal view of the head showing protuberant compound eyes and orange simple eyes (ocelli). Note the patterning on the head and the bristly antennae.

This is a psocid or barklouse - the tented wings with spots at the tips of the wing veins, plus the habitat (on foliage of trees and shrubs) make this a straightforward identification as the genus Ectopsocus. It is probably the common E. briggsi, but dissection is needed to separate it from E. petersi and E. meridionalis with ceryinaty, and the taxonomy of these closely related species remains uncertain (New, 2005). The protuberant, almost stalked, eyes mean it is probably a male.

And so, that brings us to the end of the specimens that could be identified (to some extent at least) at the time of collection about two weeks ago. However, I did mention that we would return to the eggs. Once found, I put them on their section of leaf in a small container to see if they would hatch, and they did...

Tiny larva about 1mm long - dorsal view

Ventral view showing segmented legs.

Ventral close-up of the head and thorax.

The dorsal view looks superficially somewhat like a woodlouse (i.e. it is 'onisciform'), but the darkened and hardened ('sclerotised') head with small pointed mandibles, plus the legs, show that it is actually a tiny beetle larva, one of two that hatched. It may not be immediately obvious, but this is actually a larva of a 'flea beetle', one of the small species of jumping beetles, the tribe Alticini within the family Chrysomelidae, although it might be within the wider subfamily Galerucinae within which the Alticini are included. The legs are short and have 4 segments (with a claw) and the mandibles are simple and sickle-shaped without a grinding surface ('mola'). There are thin bristles around the body (e.g. just visible top left in the 3rd photo) but no long cerci (tail-like appendages), the antennae are tiny and conical, and willows are a favourite host plant (Cooter & Barclay, 2006). Having just hatched, this is a first-stage larva and hence difficult to identify further, though van Emden (1942) is a standard work that is often useful for larval identification to family. However, the Macro-invertebrate Lab at the City Valley State University have kindly produced a Digital Key to the Aquatic Insects of North Dakota. They have good clear images of a more fully developed larva of this type, and also images of larva at genus level for Pyrrhalta - very similar to what was found here.

So, at present, I have identified all the organisms within this single leaf roll as far as I can. I hope it shows the importance of such small-scale habitats and the diversity they support, as well as highlighting some groups that are likely to be under-recorded due to their small size and tendency to hide. These under-recorded groups and habitats are worth taking the time to investigate as there are discoveries to be made that might be in your local patch of habitat or even your garden or back yard. Happy bug-hunting!

References

Cooter, J. & Barclay, M.V.L. (eds.) (2006). A Coleopterist's Handbook (4th ed.). AES, Orpington.
New, T.R. (2005). Psocids. Psocoptera (Booklice and Barklice) (2nd ed.). RES Handbooks for the Identification of British Insects 1(7): 1-145.
Redfern, M. & Shirley, P. (2011). British Plant Galls (2nd ed.). FSC, Shrewsbury.
van Emden, F.I. (1942). Larvae of British Beetles. III. Keys to the families. Entomologists' Monthly Magazine 78: 206-272.

What's in the box? No.5 - a shiny jewel and some uninvited guests.

2011-10-14T17:00:00.001+01:00

My wife is beginning to recognise the signs. A jiffy-bag lands on the doormat and there's a small box or tube inside it - yup, a specimen has arrived in the post. This time it was expected as the collector had emailed in advance to ask if I wanted a specimen or two of the colourful Rosemary Beetle Chrysolina americana (Chrysomelidae) which he had found on Hydrangea plants in a garden centre in Gloucestershire. Hydrangea is not the usual host plant - it is generally found on rosemary, lavender, sage or thyme. Of the two specimens sent, one was still alive before being sent and arrived here still very active - it is now in a pot with some sage leaves while the other has been investigated for your reading pleasure...

Dorsal view of C. americana showing the colourful stripes and double rows of punctures. Length approx 7.5mm.

The area around the suture (where the wing-cases meet) showing punctures plus some fine sculpturing.

Ventral view.

The dorsal views show what a pretty beast this is - metallic stripes on a blue background. However, the ventral view shows something less welcome in the form of numerous white tufts.

Threads of mould, plus some larger lumps, growing on the underside of the beetle.

Mould growing underneath the wing-cases which have been spread apart. The triangular structure at the top is the scutellum.

This highlights a major problem with maintaining an insect collection - the avoidance of pests which can damage specimens. With a relatively large 'meaty' beetle like this, it is important to prepare specimens to prevent mould - for example they can be dried and some people add cloves to the drying chamber to help avoid fungal growth. The next step was to see how bad the damage was.

Dorsal view with wing-cases spread.

Although the focus isn't too clear, the abdomen can be seen to be hollow with the upper surface missing and with mould coating the inside. There may have been other invertebrates feeding on the beetle as well as fungal attack.

Looking closely at the underside of the head, as well as mould, a white oval egg can be seen in the centre, below the antenna.

So, there has been some invertebrate activity - this egg was just one of several so as you'd expect, I took a closer look...

One of the eggs (mag x400) showing some small bumps on the surface. The linear structures top right are fragments of fungal hyphae from the mould.

Searching the beetle more carefully, I eventually found something that could be responsible for the eggs - a hairy mite which I think is Glycyphagus domesticus (the Furniture Mite).The pale colour and long hairs are characteristic - it used to be associated with old damp furnishings where it fed on fungi that grew on stuffing etc. So, when the moist, freshly dead beetle began growing mould, it is likely that this mite arrived to feed on the fungus.

The mite (possibly G. domesticus) on the beetle.

Of course, I don't know for certain that the eggs come from this mite. However, with the specimen in no condition for adding to a collection, I've put it in a container to see if the eggs hatch and if so, what emerges. In the end, this is a tale about the importance of preparation and maintenance of insect specimens more than my usual bug-nerding. A web search for 'dermestes' or 'museum beetle' will provide you with many unhappy tales of entomological destruction. However I don't need to repeat these so, given that I have a microscope and a camera, I thought I'd finish with a couple of shots of fine morphological detail...

The inner surface of a wing-case showing the lack of metallic colour, but with the rows of punctures clearly visible.

One of the beetle's 'feet' showing tarsal segments bearing a sickle-shaped claw and a dense brush/pad of yellow hairs. There are also other hairs and some longer, sparser bristles.

When slime gets spiky: slime-moulds of the family Didymiaceae

2011-10-10T15:34:00.001+01:00

Many people are familiar with slime-moulds to some extent, with the most popular view being of a slowly streaming patch of goo, sometimes brightly coloured, much like a large amoeba - possibly unsurprising as they are Protozoa even though commonly treated as honorary Fungi. Another comonly encountered form is the 'dog'd vomit' type which appears as a pale yellowish lumpy patch among grass, including garden lawns. One common and widespread example of this second type is Mucilago crustacea which does indeed look like dog's vomit when freshly emerged. However, within about a day, the cortex hardens and the spore mass darkens, by which time it may well have moved up the stems of grass or other plants, and become visually quite different.

The aethelium (combined spore-bearing structure) of Mucilago crustacea on the stem of a reed at Winnall Moors, southern England.

In the above picture, the dark grey-black spore mass can be seen on the left side and there is the remnant of cytoplasmic streaming beneath where the specimen has moved up the reed stem. The cortex (the surface covering the aethelium) is powdery and spongy and any movement was sufficient to send flakes and presumably spores into the air.

The cortex in close-up showing the spongy, almost brain-like, texture and powdery surface.

The reason for this texture is the presence of crystalline calcium carbonate which impregnates the structure of the slime-mould, with the cortex forming calcareous powder and flakes.

A mass of spores and calcareous crystals under x40 magnification. The dark circles are air bubbles, but note the scattered spores which appear as tiny brownish circles in transmitted light.

One of the masses under x100 magnification. A cluster of brownish spores can be seen bottom right, each being a little over 10µm in diameter. The calcareous crystals are a similar size and can be seen as small spikes to the left of the picture.

Given the presence of abundant calcium carbonate in the structure of this species, it is found most commonly in limestone-rich areas such as calcareous grasslands (Winnall Moors is a wetland on chalk) and is found only rarely in acidic conditions. The outer covering is coated with calcium carbonate in various forms (powdery, scaly, compacted and so on) in all of the Didymiaceae, the family which includes M. crustacea. The large genus Didymium has a powdery covering of star-shaped crystals which in some species may aggregate to form a crust; the shape and size of these crystals can also help to identify individual species. However, the taxonomy of this family is unclear and it is likely that genetic studies will redefine the boundaries between genera.

Reference

Ing, B. (1999). The Myxomycetes of Britain and Ireland: An Identification Handbook. Richmond, Slough. The current standard work on species in the British Isles.

Ladybirds and the fungus of love

2011-10-06T17:11:00.002+01:00

If you go into a chemist/pharmacy, the range of creams like Canestan will tell you just how familiar humans are with fungal diseases, especially sexually transmitted ones. However, humans are not the only species to suffer from fungal STDs.

One taxonomic group which is host to a fungal STD unfamiliar to most people is the beetle family Coccinellidae, the ladybirds, lady-beetles or ladybugs. In late September I was doing some conservation work, cutting willow on the wetland nature reserve of Winnall Moors on the edge of Winchester, southern England. During this work, several specimens of the Kidney-spot Ladybird Chilocorus renipustulatus were found, a scattered but sometimes locally abundant beetle associated with willow on wetlands. So, no great surprise there. I took a photo and when I got home, added it to my list of species records and also decided to add it to the iSpot site. At this point I noticed the yellowish tufts attached to the rear - I had seen two or three individuals with such tufts in the field but only now did they become clear.

C. renipustulatus showing the tufts of what appears to be H. virescens on the rear of the elytra (wing cases).

I had no idea what they were (they looked like lichen but that seemed unlikely!) and made a note to investigate, though I didn't have a specimen. However, a few days later, one of the recorders from the UK Ladybird Survey posted a response stating that the tufts looked like the sexually-transmitted fungal disease Hesperomyces virescens (in the order Laboulbeniales). This was interesting enough as I'd never heard of it, but he also mentioned that it might be the first record of H. virescens on this species of ladybird. A shame I didn't collect a specimen! So, what is this fungus and what does it do?

All the fungi in this order are obligate parasites of arthropods (i.e. they need live arthropods) and derive nutrition via a 'haustorium' which penetrates the cuticle (Evans 1988). So, although they are ectoparasites (living on the outside of their host), they do penetrate the surface and H. virescens is in fact one of the few fungi in this order to have haustoria forming a number of narrow branches radiating out into the body cavity (Batra 1979). In work on the first record of this fungus on the Harlequin Ladybird Harmonia axyridis, Garcés & Williams (2004) noted that H. virescens was more prevalent in autumn after ladybirds had been through a period of aggregation/clustering. With my observation having been made in late September in the UK, this tendency may explain that a few fungal tufts were noted even though they weren't being sought.

Other ladybird species such as Adalia bipunctata (the Two-spot Ladybird) and Olla v-nigrum (the Ashy-Grey Ladybird) have been recorded as hosts of this fungus, while research into a relative of the species considered here, C. bipustulatus (Heather Ladybird), has shown that the fungus can cause premature death of the beetle (Kamburov et al. 1967). More recent work in the US (Riddick & Cottrell 2010) has suggested a preference for H. axyridis as a host with few instances of the fungus infected its 'original' host Hippodamia convergens (the Convergent Ladybird), a common and widespread species in North America. However, this research notes that H. axyridis was also the most abundant ladybird, hence the high rate of fungal infection could be due to the higher frequency of sexual/social contact between individuals (this was also seen in the native O. v-nigrum) - something which is reduced in less abundant species. Both H. axyridis and O. v-nigrum overwinter is mixed-sex aggregations, again supporting the idea that host and fungal abundance are connected. This may seem obvious in hindsight, but is important as it also links to possible effects due to differing activity levels.

For instance, Riddick & Cottrell (2010) also showed that of the two main host species, H. axyridis males had a higher infection rate than females, something not seen on O. v-nigrum. This suggests a possible behavioural effect with H. axyridis males behaving in such a way (they mount males as well as females when seeking mates) as to experience greater levels of exposure to the parasite. When Welch et al. (2001) proposed their sexual transmission hypothesis to explain the distribution of H. virescens thalli on ladybirds (they looked at A. bipunctata), this was because they noted fungal structures on the upper surface of females and the corresponding underside of males, mirroring the mating position. As physical contact may initiate spore discharge, the position of the fungus on a beetle's body may reflect the type of contact that occurred
(Weir & Beakes 1996). Thus, fungal infection rate may be affected by the rate of sexual/social contact as well as simply the abundance of hosts.

So, we have an overview of some aspects of the relationship between the fungus and several ladybird hosts, but what about C. renipustulatus? Well, initial indications are that there are no published records of this ladybird as a host of H. virescens. This may turn out not to be the case even though I have searched quite thoroughly as has 'rimo' at iSpot, but for now this appears to be a potential new discovery worthy of a visit to Winnall to collect specimens!

*** UPDATE ***
After feedback from mycologists, this find does appear to be a world's first as a new host for the fungus and has now been published as a short paper in The Coleopterist:

D. Hubble (2011). Kidney-spot ladybird Chilocorus renipustulatus (Scriba) (Coccinellidae), a new host for the parasitic fungus Hesperomyces virescens Thaxter (Ascomycetes: Laboulbeniales). The Coleopterist, 20 (3), 135-136 Other: 0965-5794

References

Batra, L. (1979). Insect-fungus Symbiosis, Nutrition, Mutualism and Commensalism. Allenheld, Osmun & Co., New York.
Evans, H.C. (1988). Coevolution of Fungi with Plants and Animals. Academic Press, San Diego.
Garcés, S. & Williams, R. (2004). First record of Hesperomyces virescens Thaxter (Laboulbeniales: Ascomycetes) on Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae). Journal of the Kansas Entomological Society 77(2): 156-158.
Kamburov, S.S., Nadel, D.J. & Kenneth, R. (1967). Observations on Hesperomyces virescens Thaxter (Laboulbeniales), a fungus associated with premature mortality of Chilocorus bipustulatus L. in Israel. Israel Journal of Agricultural Research 17(2): 131-134.
Riddick, E.W. & Cottrell, T.E. (2010). Is the prevalence and intensity of the ectoparasitic fungus Hesperomyces virescens related to the abundance of entomophagous coccinellids? Bulletin of Insectology 63(1): 71-78.
Weir, A. & Beakes, G.W. (1996).Correlative light- and scanning electron microscope studies on the developmental morphology of Hesperomyces virescens. Mycologia 88: 677-693.

Welch, V. L., Sloggett, J. J., Webberley, K. M. & Hurst, G.D.D. (2001). Short-range clinal variation in the prevalence of a sexually transmitted fungus associated with urbanisation. Ecological Entomology 26: 547-550.