Eight spores good - a mossy mystery

Looking through moss and fragments of moist dead wood recently, I've found a range of small invertebrates such as mites, and spurred on to see what else dwells within, I've clocked up some more microscope time. Scanning a specimen of the creeping feather-moss Amblystegium serpens, a common species known from various habitats/substrates including both living and dead wood, I noticed some tiny red-brown structures underneath some of the leaves. Having a look through Atherton et al. (2010) and Watson (1981), no moss structures looked quite like it, so I started photographing and magnifying...

Structures growing from the stem of Amblystegium serpens

There's not a lot of detail here, but an idea of scale can be gained - the width of the stem (no more than about 0.2mm - the leaves are also tiny, about 0.5mm long) is clear where it reaches the left-hand side of the photo and the more-or-less rectangular (but not especially elongate) individual cells can be seen there. Just to the left of the pin, the stem is a little different however - the cells are orange-brown and a little larger. This might be of interest as many gall-causing Fungi induce changes in cell size and tissue colour. So, to see more detail in the brown masses, I made a simple 'squash' preparation for higher magnification.

Fibrous structure growing from the stem beneath a leaf of Amblystegium serpens

The fibrous structure is clearer here, including its point of attachment/outgrowth from just below the base of a leaf. The longest fibres are maybe 0.5mm long, maybe a little more, but it is still unclear exactly what they are. Mosses produce a number of structures worth considering here:

• Paraphyses - thin sterile hairs, sometimes club-shaped, usually multicellular. A possibility.
• Protonema - the young stage of a moss that develops when a spore germinates; generally appears as a system of green threads. Clearly not the case here.
• Gemma - a unit of vegetative propagation, may be single-celled, two-celled or multicellular. Another possibility.

To determine whether these were parts of the moss and/or a fungus growing on it, more detail was needed.

Various structures seen attached to Amblystegium serpens

A fungal spore found with a sample of Amblystegium serpens

In the first of this pair of photos, a number of structures are visible. Those indicated by blue arrows are unidentified - the larger fragment could be a paraphysis or similar (or an equivalent fungal paraphysis) while the 4-celled structure could be gemmal or a 4-celled fungal ascus (spore-bearing 'sac') - this is largely guesswork however, partly informed by checking fungal structure using Webster (1970). The structure indicated by a red arrow is rather clearer and appears to be the ascus (spore-bearing 'sac') of a discomycete fungus, complete with the typical eight spores seen when fully developed, though the left-most one is blurred out in the photo. Other similar structures could be seen, including the spore in the lower photo - it is almost spherical and measures around 13 x 15 um, and although again blurred out here, has a surface covered in tiny 'warts' (i.e. it is 'verruculose'). Consulting Ellis & Ellis (1998), there appears to be only one contender with this host and set of characteristics - the microfungus Octospora wrightii which is associated primarily with this moss, and is found from January to March.


As ever, comments, suggestions and corrections welcome - I am, as is so often the case, writing outside my comfort zone here; how else to learn though?


References

Atherton, I., Bosnaquet, S. & Lawley, M. (eds.) (2010). Mosses and Liverworts of Britain and Ireland: A Field Guide. British Bryological Society. [If you only buy one UK bryology book, I can recommend making it this one]
Ellis, M.B. & Ellis, J.P. (1998). Microfungi on Miscellaneous Substrates: An Identification Handbook (2nd ed.). Richmond, Slough.
Watson, E.V. (1981). British Mosses and Liverworts (3rd ed.). Cambridge University Press.
Webster, J. (1970). Introduction to Fungi. Cambridge University Press.

Sighting the mighty tiny mite

A couple of days ago, I mentioned oribatid mites, more-or-less in passing while looking at other moss, soil and decay fauna. As they are so important in the processes of decay and decomposition, feeding on all sorts of organic matter, I decided to return to my samples and see what else I could find. Unsurprisingly I found a few more but although I can't identify them to species (yet - I'm starting to have a look at Michael (1888) which you can download for free here), I thought it would be a good opportunity to give a bit of introductory information about this often unfamiliar group. So, what are oribatids?

Taxonomically, they form the order Oribatida within the Acari (mites) which are in turn arachnids. All are small (none more than 1.4mm in length) and those that I found were between 0.5 and 1.0mm. They are largely found in soils (especially in woodlands) and decaying matter (dead wood, leaf litter etc), and are important in soil processing and formation in much the same way as earthworms. Like other arachnids they have jaws known as chelicerae, and are eight-legged, but some other features may not be familiar.

Oribatid mite, approx 0.7mm long, ventral view

The pteromorph is a wing-or cloak-like extension of the carapace which wraps partly around the mite, presumably to armour it against damage from soil particles or predators. The genital shield is a round structure formed of two semi-circular halves which covers the reproductive structures - males have a penis-like structure called an aedeagus, much like that seen in beetles. Similarly, the anal shield is paired and covers the end of the gut.

Oribatid mite, approx 0.7mm long, ventral view

Unlike the more familar red spider mites (Trombidium spp.), these are not hairy/velvety but are smooth with only fine sculpturing and sometimes larger but fewer bristles. The legs do however have long bristles which perform a sensory function, and in fact the first pair of legs of some species are purely sensory (like antennae) and are no longer used for locomotion. There is a single median eye and with vision reduced (unsurprisingly as oribatids are mainly soil-dwelling), sensory bristles have become more important, not just on the legs, but also via the development of specialised bristles to form a 'pseudostigmatic organ' which can have a variety of shapes e.g. club or drumstick.

That is all the detail I can provide at present without simply summarising Michael (1888) and covering features not visible in my photographs. However, I am sure oribatids will show up on my invertebrate radar again, and I hope to be able to delve more deeply into their ecology and taxonomy.

Reference

Michael, A.D. (1888). British Oribatidae Vol.II. Ray Society, London.

Tiny denizens of the rot-hole

What with winter keeping most invertebrates out of sight, it's been a while since I wrote much of an entomological nature, but yesterday was a fine opportunity to head up to Beacon Hill nature reserve to see what was about. As well as chalk grassland (which will be more interesting when in flower), there is an interesting stand of beech woodland and associated scrub, including an ecologically important resource of dead wood (standing and fallen) and old mossy trees.

The base of a mossy beech tree.

These features mean that there is habitat for many fungi and dead-wood invertebrates and the evidence is everywhere - beetle boreholes (some opened by woodpeckers, one of which could be heard clearly in the woodland), wood in various stages of decay, insect-feeding birds such as a treecreeper (Certhia familiaris) and an intriguing-looking rot-hole with a large fungus and a tuft of hair poking out of it...

Rot-hole with fungus and tuft of hair

Looking inside, it had been lined with moss and hair, and was clearly a nest or roost of some sort, either of a bird or small mammal, and the fungus is (I think) an oyster mushroom Pleurotus ostreatus - if any mycologists would like to correct me on this, please do!

The inside of the rot-hole; at the base of the fungus, a layer of moss-and-hair bedding.

So, sample-pot in hand (like any good ecologist!), I took a pinch of the mossy bedding, including some soil/decayed wood from directly beneath it - after all, there are plenty of under-recorded parasites that live in vertebrate nests and you never know what you'll find. Back home, it was time to check what I'd found; some of the small inveretebrates such as Collembola (springtails) hide very effectively in material like this, so I find that adding some water to the sample in a watch-glass causes them to float to the surface and become easier to see. Indeed, doing this brought up a cluster of the common springtail Ceratophysella bengtssoni which can sometimes be found in large aggregations on the surface of soil and puddles, but may well still have been hibernating given the cold night-time temperatures at present.

Several Ceratophysella bengtssoni from the nest sample

These weren't the only springtails - Lepidocyrtus cyaneus and Neanura muscorum were also present, as was Tomocerus vulgaris from mossy dead-wood of a nearby tree. The samples included quite a few empty moulted skins, suggesting that these are not solely hibernation sites, but places where active feeding and growth occur - unsurprising as they mainly feed on fungal hyphae and decaying plant material (no shortage in this sample location). They are also an excellent group to look for in the winter as they can be found throughout the year - if you are interested in the UK species, Hopkin (2007) is an excellent place to start. However, Collembola are not the only soil/leaf-litter animals to be found. Hidden among the tangle of hair (mainly sheep I think) and plant fibres were two shed skins of an oribatid soil mite.

The shed skin of an oribatid soil mite

Oribatids are beyond my identification skills (I don't even know anyone who can ID them, though I do have a go at halacarids occasionally), but the shiny bulbous shape, the pointed mouthparts and the leg attachment points are all visible here. Though poorly known outside the realm of specialists, these mites are important in the decay process, feeding on a wide range of plant, animal and fungal organic material, with a minority being predatory - in fact they break down and process soil material in a similar way to earthworms even if they aren't as familiar or well-understood/studied.

Another species, common if often over-looked, and mainly found under bark or logs in woodland is the spotted snake millipede Blaniulus guttulatus. It is often considred a pest (e.g. in allotments) but probably only enters crops when damage has already occurred, such as by a 'primary' pest or some other mechanical means. They grow to around 20mm in length and are white with rows of red spots along the sides. The specimen I found however was a juvenile no more than about 3mm long (with few segments/spots), and the first early stage I've seen of this species.

Juvenile Blaniulus guttulatus

So, a few interesting finds - common species (no idea about the oribatid) but indicative of the small and often un-noticed soil/dead-wood fauna. Interestingly there were no mammal/bird nest-dwelling species (such as ticks or fleas), and no indication of exactly what had been using the hole - however, the presence of fine hairs and small dark elongate faeces, plus a lack of even small feathers suggest a mammal, presumably a rodent, rather than a bird.

Reference

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

Flit, flutter and flirt

Today it may be cold, grey and sleeting, but yesterday was clear and sunny, and provided me with the opportunity to watch the 'spring-is-coming' behaviour of a pair of familiar garden birds - blue tits (Parus caeruleus, sometimes put in the genus Cyanistes). There have been blue tits around throughout the winter, making good use of feeding opportunities (I am their 'food monkey'), but they have been doing little more (as far as I can tell) than feeding, hiding/roosting and basically surviving.

A pair of blue tits investigating our garden

A small, charismatic species, blue tits are well known for their acrobatic feeding habits, but what was particularly noticeable yesterday were bursts of frantic darting and chasing, barely stopping for a second.

After a brief pause, back to darting about...

This is, I can only imagine, mating/flirting behaviour - plenty of species engage in some sort of chasing, and spring is soon due to, well, spring. Also, there were other behaviours, including female fluttering which echoes the food-soliciting movements of juveniles, and male calling which seems likely to be a precursor to more strictly territorial singing.

A fluttering female

A calling/singing male

Punctuating the more obvious flirting there were periods of feeding which may be somewhat ritualised, where one or both would pick at parts of the fence and perform various feats of acrobatics. Maybe I'm anthropomorphising a bit, but at times it did look as if one was hiding while the other fed (or pretended to) and then chased it - repeat until pair-bonded?

Busy feeding (or feeding-like) behaviour

That's all from me for now - less technical, more illustrated than my usual posts, but all kinds of topics are in the pipeline...