Lovely little loofahs

As I have a static page devoted to dead wood monitoring at habitat/woodland scale, the organisms associated with dead wood do appear on my blog from time to time. On this occasion, I'd been tidying up the 'wrecking yard' at the far end of our garden where I cut firewood and so on. Because of this, unwanted offcuts that are too decayed to be useful have been piled up to form habitat for saproxylic (dead wood) species. Often these may be small invertebrates such as beetles and barklice, but of course, Fungi are also important in the decay process, as are myxomycetes (slime moulds) which, although often included as 'honorary Fungi', are actually Protozoa. As a group, 'myxos' are widespread - everywhere which some suitable substrate, though they often remain unseen as their fruiting bodies are often very short-lived. So, I was interested to see some clusters of small loofah-shaped growths on small rotting logs.

The myxomycete Arcyria obvelata - approx 1cm tall

Having a copy of Ing (1999) made identification pretty straightforward - Arcyria obvelata is a common species on dead wood, especially beech, sometimes oak, and occasionally (as here) on conifers. It is typified by the short stalk leading to a funnel-shaped cup upon which there is the tall, pale yellow sporangium of tangled tubes bearing minute spores, the whole being up to 15mm tall. When newly grown, the sporangium is a short, smooth cylinder, but when mature it expands as seen here with the longer ones drooping.

Apparently there are some colour variations, but these have not yet been found in Britain - maybe something to look out for!

A larger clump of Arcyria obvelata

Reference

Ing, B. (1999). The Myxomycetes of Britain and Ireland: An Identification Handbook. Richmond, Slough.

Teeny-tiny toadstools - or are they?

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.

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

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.

Glassy fingers, orange goo and scrambled eggs: tree-stump slime-moulds

A definite departure from my usual taxonomic interests today as I look at some slime-moulds associated with tree-stumps. Traditionally, the slime-moulds (or Myxomycetes) have been included within the Fungi, but - with mitochondria and tubular cristae in their cells - are actually members of the Protozoa. However, as their habitats, spore dispersal and methods of study are similar to those associated with true Fungi, they are often still considered 'honorary' Fungi for everyday purposes.

High-level taxonomy aside, the slime-moulds are, to many people, an unfamiliar and mysterious group of organisms even though many are distinctive and, during their 'plasmodium' stage quite large - some, weighing 20kg or more (yes, 20kg) and covering/filling whole logs, may even be the largest single cells known. However, most are smaller but still have a plasmodium several centimetres across and often brightly coloured. Most species live in woodlands in the sorts of microhabitat often associated with Fungi - the focus here is on just one of these, tree-stumps. In fact, the first three species were all found on a single stump in the New Forest just a couple of days ago:

Tubifera ferruginosa (the patch is about 4-5cm long). This specimen is clearly orange; others may be more pinkish giving this species the not always accurate common name 'Raspberry Slime Mould'. It darkens as it ages, and sometimes looks rather like a strawberry. But not a raspberry. Hey ho - this is why we use scientific names... The individual 'pimples' are the tops of cylindrical sporangia (spore-bearing structures) and this species is common during late summer and early autumn throughout Britain.

The bright yellow plasmodium of Fuligo septica, somewhat reminiscent (to me at least) of scrambled egg. The main mass here is about 5cm across and you can see some of the thin threads produced by 'cytoplasmic streaming' as the organism stretches and flows across the surface. This species is found as far north as Yorkshire, but has a scattered distibution, mainly in south-east England.

The transparent, glassy/watery 'fingers' of Ceratiomyxa fruticulosa. Each finger contains the spore-bearing structures and is a few millimetres tall, to a maximum of maybe 1 cm. This is another common widespread species - in Britain found from early summer onwards.

A closer view of C. fruticulosa.

Earier in the year, in June, I found some other myxomycetes which exhibited quite a different structure.

Brown slime-mould structures, like eggs in a nest.

Here they are emerging and also showing orange and reddish colours.

More examples of orange structures.

A close-up of an orange-red structure emerging from a crack in a stump.

These four pictures are all of slime-moulds of the Lycogala epidendrum group, a complex recently split into two species, L. epidendrum and L. terrestre. Microscopic examination (e.g. of the spores) is needed to separate them, so for the purposes of this post, I shall simply call them Lycogala. In these species, the spore-bearing structures are effectively fused to form an 'aethelium' several millimetres across which can be greyish, brownish or pinkish - the 'eggs' seen above. Like F. septica, Lycogala can escape from dead wood via holes such as those made by beetles as well as through existing cracks and crevices. The plasmodium is reddish or pinkish as seen in the lower picture as well as near the right-hand edge of the second picture.

Now, I am no expert on slime-moulds, but I do find them intriguing - and it's quite a sight when several brightly coloured species inhabit the same piece of dead wood. However, I can recommend the excellent handbook by Ing (1999) which I am highly reliant on - it won't give you lots of colour photos (though a web search will), but it does provide simple line drawings of key structures, keys, spore measurements and so on covering the few hundred species in Britain. It's also the first comprehensive work on the British species since 1877! 

Enjoy the slime!

Reference

Ing, B. (1999). The Myxomycetes of Britain and Ireland: An Identification Handbook. Richmond, Slough.