Keys to Fungi on Dung
|Transcriber's note:||Corrigendum applied at the wish of the principle author: in Key 3 the pointers to couplets 56 and 66 were the wrong way round and have been corrected in this edition.|
KEYS TO FUNGI
M. J. RICHARDSON
165 Braid Road,
EDINBURGH EH10 6JE
Royal Botanic Garden,
EDINBURGH EH3 5LR
Published by the British Mycological Society
PO Box 30, Stourbridge
West Midlands DY9 9PZ
© British Mycological Society 1997
Printed in Scotland by BPC-AUP Aberdeen Ltd
ISBN 0 9527704 2 3
The first edition of these keys was published in the Bulletin of the British Mycological Society 2, 18-43 (1968) and 3, 86-88, 121-124 (1969) in an attempt to bring together in one place information for the identification of coprophilous fungi which would be useful to teachers and others interested in these fungi. They were issued as a separate publication in 1972, and with corrections in 1974. They were reprinted in 1982 with additions. This latest edition is an update of all the earlier ones, with current nomenclature and recent references, and the inclusion of some additional species.
Coprophilous fungi are highly satisfactory for demonstrating the diversity and morphology of a group of related organisms within an ecological system. Representative genera of most major groups of fungi can usually be guaranteed to appear on dung after a period of incubation. There is no shortage of dung in our fields and woods, and this material will always produce characteristic fungi at whatever time of year it is collected.
Dung is best incubated in a light place, for example on a table in a warm room, on layers of moist filter paper or other absorbent material. For rabbit pellets, and samples of similar size, Petri dishes are ideal; for horse 'apples', and larger types of dung, large covered dishes such as glass casseroles, plastic sandwich boxes or yoghurt pots are needed. The top third cut from a plastic lemonade or mineral water bottle fits neatly in a Petri dish, and replacing the screw cap with a cotton wool plug allows aeration and gives adequate height for developing basidiomycetes. Samples should not be kept in airtight containers for any length of time after collection, as in such conditions insects and nematodes tend to break down the dung, and anaerobic conditions which do not favour the fungi rapidly develop. If they cannot be set to incubate soon after collection they can be gently air dried, as most dung fungi will remain alive after such treatment and grow out when the sample is eventually moistened. The absorbent material should be kept moist. Although free water will not allow the best development of ascomycetes, the succession of basidiomycetes appears to vary with the wetness of the dung. Earthworms and insect larvae should be excluded from the samples as far as possible, for they break up the dung too much; activity of the latter can be reduced by spraying lightly with a household insecticide. If space is limited and cultures are kept nearby, it is very important to prevent mite infestation. Containers can be isolated by placing on glass plates lightly smeared with Vaseline, to which an acaricide (e.g. methyl benzoate) can be added.
Fungi are best sought with a stereoscopic binocular microscope, when their full beauty will be seen, but a hand lens or simple magnifier, although less convenient, is sufficient for all but the smallest forms. The larger ascomycetes and most of the basidiomycetes are readily seen with the unaided eye, but the binocular microscope is still very useful for observing the gross features of the veil of the basidiomycetes. Perithecia, apothecia and similar structures can be removed with fine needles or forceps quite cleanly for mounting, initially in water, on slides. Subsequent irrigation with iodine solution will allow any reaction of ascus wall, tip or pore to be observed, and mounting in diluted Indian ink can enhance the visibility of appendages, caudae and sheaths which occur on some spores. Spore discharge in the ascomycetes often occurs from mature asci when material is mounted in water, so mature spores can immediately be seen. Many of the coprophilous toadstools (agarics), because of their small size and/or rapidly deliquescent nature, often do not give spore prints in the normal way, but mature spores can usually be found on the stipe or in natural spore prints formed on the absorbent material on which the dung is supported. For accurate identification the ability to measure the size of spores and other structures will be necessary. Basic microscopical technique and mycological knowledge is assumed. Common species are well described and illustrated in popular books, and references are given to specialist works to allow descriptions of less common species to be found. It will be necessary to refer to these for critical taxa. Although this edition contains about one half more species than the 1982 edition, there are still many species to be described and new records and observations to be made, especially in the Ascomycotina.
Four keys are presented. Keys 1 and 2 (MJR) are to the coprophilous ascomycetes, a very diverse group which, although not covering all the possible types of reproductive structure found in the class, contains many of the important types. The information for the identification of these fungi is dispersed throughout the literature, and many new species are still being discovered and described. Some appear to be world-wide in their distribution, others more restricted, with a prevalence of reports from either arctic, temperate or tropical regions. These keys are not exhaustive, since there are far too many species to make it practical to include them all. They do, however, include most genera, and the commoner or well known species of temperate regions. Specific (and even generic) limits in some cases (e.g. Coprotus / Ascophanus / Ryparobius / Thelebolus) are still the subject of debate and the choice of names to use in the key for a few taxa has been a compromise. Key 2 includes the original 'plectomycete' key (RW), which contains fungi which may not be strictly coprophilous in the normal sense, but fungi which occur on hair, horn, bone and cadavers, and may thus be found on carnivore dung or pellets of owls and other birds of prey.
Key 3 (RW, p. 52) is to the basidiomycetes of dung and associated debris. The part of the key dealing with the agarics attempts to be as complete as possible. Since the toadstools have always been thought of as the best known of the coprophilous fungi, attention to their taxonomy has often been careless. In this key the opportunity has been taken to adopt a rather narrow species concept, and to provide in certain places indications of where distinct taxa, even autonomous species, may be found after further laboratory work. Many of these types have been cultured and appear to differ vegetatively in ways which support observations of gross morphology. Coprophilous agarics are popular material for genetic studies and additional information on veil structure, spore number etc. of individual species is given, even when these are not 'key characters'.
Key 4 (MJR, p. 63) is to the Zygomycota (phycomycetes) which are characteristic of dung and amongst the first to appear when freshly dropped dung is incubated. They soon disappear, however, but their fruiting can be prolonged by plating small portions of dung on a nutrient medium (e.g. potato carrot or potato dextrose agar) to which has been added a small amount of antibiotic to reduce bacterial growth. This method is especially suitable for the parasitic and predacious fungi. A cultural approach is essential for the identification of many of these fungi and the above media, and oatmeal agar, are suitable for culture as well as isolation. For this reason the study of this group of fungi is less easy than that of the ascomycetes and basidiomycetes but, because the asexual stages are characteristic, we have attempted to key out the commoner genera which might be found, with notes on common species. The asexual spores are sporangiospores formed in sporangia; some sporangia produce a single spore within a closely fitting sporangium, and have in the past been erroneously described as conidia. A great range of sporangial structure occurs within the orders concerned. The classical structure is the massive (up to 250Ķm diam.) multispored sporangium with an internal columella which remains after the spores have been dispersed (e.g. Mucor); those of Mortierella are similar, but smaller and without a columella. Other sporangia are much reduced and may be only 10-20Ķm diam., and contain only a small number of spores (Thamnidium) or one spore (Chaetocladium); these small globose structures are termed sporangioles. Spores may also form in chains; the chains are in terminal groups and are formed by the differentiation of the contents of cylindrical sporangia which are considered to be part-sporangia (merosporangia). When the sporangial wall has disappeared the spore chains may remain discrete and intact, or they may collapse into a wet droplet of spores (Syncephalastrum, some Piptocephalis). Members of the Kickxellaceae (e.g. Coemansia, Kickxella) have single spored merosporangia produced in serried ranks on boat-shaped or swollen structures (sporoclades). The sexual spores (zygospores) are rarely seen without culturing; oatmeal agar is one which favours their production. The key includes one member of the Entomophthorales, which also produces single-spored sporangia. Other members of this order may be found parasitising the various animals which live in dung; many other predacious fungi may also be seen, e.g. parasites of amoebae (Acaulopage). The key is of necessity far from complete, and omits members of the Dimargaritales, which have been found frequently on dung of small mammals in America.
Mitosporic fungi ('Fungi Imperfecti') and myxomycetes have been excluded, since they would expand the range of these keys beyond what was initially intended, although numerous species of both groups occur on dung when incubated in a damp chamber. For mitosporic fungi see Seifert, Kendrick & Murase (1983) and Ellis & Ellis (1988); for myxomycetes see Eliasson & Lundqvist (1979). As practical keys, rather than a taxonomic treatment, taxonomic authorities have not been cited. For ascomycetes, Cannon, Hawksworth & Sherwood-Pike (1985) have been followed, unless there is a more recent treatment of a group. For the basidiomycetes the 'New Checklist of British Agarics and Boleti' (Dennis, Orton & Hora, 1960, Supplement to the Transactions of the British Mycological Society 43) has been followed, and The British Fungus Flora (Orton & Watling, 1979 and Watling, 1982).