Grey Shag

The Grey Shag is one of the classic dung and compost inkcaps, a member of Coprinopsis in the family Psathyrellaceae. Like most of its relatives it practises autodigestion: rather than drying out and shedding spores slowly, the cap deliquesces from the margin upward, the gill tissue liquefying into an inky black fluid that carries mature spores away as it drips.

Beyond the field, Coprinopsis cinerea is one of the best-known fungi in the laboratory. Its short life cycle, ease of cultivation on simple substrates and neat, well-behaved fruiting have made it a standard model organism for studying how mushrooms develop, how mating types work in basidiomycetes, and how light and temperature trigger fruiting. Few wild-collected agarics have had their genetics examined in comparable depth.

In the field it is recognised by its habitat and by the loose, greyish-white woolly coating of universal veil that clothes the young cap. That veil is much less shaggy than the coarse upright scales of the true shaggy inkcaps and much less silky than the flat, mica-like granules of Coprinellus, giving the young fruit body a felted, slightly unkempt look that suits its English name.

Cap

At first ovoid to cylindrical, 2-5 cm tall, expanding to conical or bell-shaped and finally splitting and revolute along the margin. The ground colour is pale grey to greyish-brown, darker over the disc, and the whole surface is covered when young in a whitish to grey woolly-fibrillose universal veil that soon breaks into loose flakes and patches, often washing off entirely. Fine radial grooves develop as the cap expands. Within a day the margin begins to blacken, curl and liquefy.

Gills

Free or very narrowly attached, extremely crowded and thin, white at first, then passing rapidly through grey to inky black as spores mature. Deliquescence begins at the gill edges and works upward, so the gills are frequently seen half-dissolved with black droplets hanging beneath.

Stipe

Slender and tall in proportion, 5-12 cm long and only 2-5 mm thick, white, hollow, fragile, finely fibrillose to almost woolly toward the base. There is no persistent ring, though remnants of veil sometimes cling near the base. The base is slightly swollen and often tapers into a short pseudorrhiza rooting into the substrate.

Flesh & spore print

Flesh very thin, whitish, without distinctive odour. The spore print is black. Microscopically the spores are smooth, dark blackish-brown and ellipsoid with a central germ pore, a standard combination for the genus.

Almost always tied to material rich in decomposed manure: horse and cattle dung heaps, spent mushroom compost, rotting straw and hay, garden compost bins and manured beds. It also appears in greenhouses, on stable bedding and on heaps of decaying vegetable matter, and its tolerance of relatively warm conditions means it can fruit indoors and out of the normal season.

Distribution is effectively worldwide, following agriculture and animal husbandry. In cool temperate regions the main flush is from late spring through autumn, but in heated compost or under cover it may fruit at any time of year. Fruit bodies typically appear in scattered troops or small clusters and rarely last more than a day.

Coprinopsis cinerea is a saprotroph, and specifically a coprophilous and compost-inhabiting one. Its mycelium colonises the partially digested plant fibre in dung and manure-enriched straw, breaking down cellulose and other polysaccharides that have already passed through a herbivore gut and a bacterial fermentation stage. It is a secondary coloniser, arriving after the first wave of moulds and ascomycetes.

The deliquescing cap is an adaptation to this crowded, ephemeral habitat: by liquefying, the fungus releases spores in a dense black fluid over a compressed period, and those spores are readily splashed, carried by flies or ingested by grazing animals to be deposited in fresh dung elsewhere. Its role in the ecosystem is essentially one of rapid nutrient turnover, converting bulky organic waste into fungal biomass and freeing minerals back into the soil.

Coprinopsis lagopus, the Hare'sfoot Inkcap, shares the woolly veil but is even more fragile, is generally grey-white with a distinctly hairy young cap, and grows on woodchip mulch and leaf litter rather than dung. Coprinopsis nivea is also a dung specialist but is coated in a chalky, powdery pure-white veil that gives it a floury appearance quite unlike the grey felted flakes of the Grey Shag.

Coprinopsis atramentaria is much stouter, with a smooth to finely scaly grey-brown cap lacking a woolly coat, and grows in dense clumps from buried wood in grass and along paths. Coprinus comatus is far larger, with a tall cylindrical cap broken into coarse upturned shaggy scales and a movable ring on the stipe, and prefers disturbed grassland rather than manure heaps.