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...
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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.
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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.
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Various structures seen attached to Amblystegium serpens |
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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.
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