"No one likes changing diapers, or cleaning up after the dog has relieved itself on the neighbour's lawn. So why would anyone condemn themselves to spend hours poised over a dish of dung, scrutinizing it through a microscope? Most people who find themselves in this situation have signed up for a mycology course, and have been assigned this sordid task by a professor who they might initially suspect of being sadistic and possibly perverted.
Since most readers of this key will probably be students who have just been thrust into this very situation, may we at once urge you to put behind you any irrational urge to chuck the whole thing and register in another course. There are excellent reasons for studying dung.
Dung is of great concern to the human race, individually and collectively. Its periodicity is widely considered a barometer of physical health, and it can reveal the presence of parasites and diseases. Freudian analysts apply such labels as 'anal retentive' to their neurotic clients. Hucksters for proprietary medicines rave about 'regularity' and 'inner cleanliness.' Comedians have thrived for generations on scatological humour. And just as the lnuit have many words for snow, we have a plethora of epithets for excrement, ranging all the way from the gutlessly genteel to the egregiously gross.
All free-living animals produce dung in one form or another, and they do so at fairly regular intervals. Herbivores and detritivores, particularly, defecate on a rather grand scale. And yet the world has not disappeared under a great wave of the stuff. For this, much thanks -- but to whom or to what? Largely, we must thank the inefficiency of the digestive process in most animals. This ensures that the discarded dung remains an excellent source of nutrients for other less fastidious organisms -- it is often, for example, very rich in nitrogen. And, as always, where food is regularly available, organisms have evolved to exploit it...
Students of mycology look at dung because it is the home of a large community of fungi -- the so-called coprophilous fungi. These organisms have highly specialized strategies and structures that can often be easily seen and understood by students. Although mostly microscopic, dung fungi include some of the most spectacular members of their kingdom. There are some amazing zygomycetes, especially Pilobolus, the hat-thrower, which aims and shoots its sporangia up to 2 metres toward the light. There are 175 genera of ascomycetes, including many which have light-seeking (or phototropic) mechanisms built into the tips of their asci, or the necks of their perithecial ascornata, so that their spores can be shot away from the dung... There are also a number of basidiomycetes, mostly of the agaric genus Coprinus, which conduct chemical warfare against the hyphae of other fungi, and after vanquishing them, produce wave after wave of delicate and beautiful but ephemeral mushrooms that rain dark spores into the air...
But there is another almost unknown group of coprophilous fungi, even less conspicuous, and lacking the ability to shoot their spores, but very numerous and often abundant on dung. These are the hyphomycetes, conidial fungi that are asexual forms, or anamorphs, of many Dikaryomycota. There are keys to all the other groups of dung fungi (Richardson & Watling, 1968, 1969), but until now there has been no compilation devoted to the coprophilous conidial fungi. Hyphomycetes are common on the dung of most animals, and why they are not mentioned in the majority of papers is not clear. There may be a feeling that hyphomycetes are not true dung fungi, but contaminants arriving from the air or soil, after the dung has been deposited. The fact that some hyphomycetes are known only from dung shows that this is not a justified assumption. There may also be a feeling that such inconspicuous organisms cannot play a significant role in dung ecology. Again, since dung may become completely covered with species of such genera as Arthrobotrys, Basifimbria or Oedocephalum, this is not so.
The study of hyphomycetes on dung offers many things to the student. There are a number of fantastic forms among the coprophilous hyphomycetes, which would be fascinating purely for their visual splendour. Nematodes and nematode-trapping fungi are common on dung, and by consulting the book The Nematode-Destroying Fungi (Barron, 1977), a student can gain some first-hand experience with this unique group. Some fungi may produce both asexual and sexual reproductive structures on dung: for such anamorph-teleomorph pairs, DiCosmo & Kendrick (The Whole Fungus, 1979) should be consulted. Our 200 illustrations give only a hint of what is in store for the keen-eyed, mycophilic student."
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