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 250µm
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 10-20µm 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).