Panaeolus cyanescens
Panaeolus cyanescens
Also called copelandia cyanescens, blue meanie, blue foot mottlegill
A slender pale-capped dung mottlegill of warm regions whose flesh and stipe stain blue-green where handled, with mottled black gills and a black spore print.
Overview
Panaeolus cyanescens, long placed in the segregate genus Copelandia, is a small pantropical dung agaric best recognised by the strong blue to blue-green discolouration that appears wherever the fruit body is bruised or handled. The epithet cyanescens simply records that colour change.
In other respects it is a typical mottlegill: a thin, pale, hemispherical cap on a long slender stipe, with gills that ripen unevenly to a marbled black and a jet-black spore deposit. What separates it in the field from the other pale dung species of the genus is the bruising reaction, which develops within minutes on the stipe base and cut flesh.
It is a fungus of warm grazing land, following cattle and horses across the tropics and subtropics, and is one of the most widely distributed dung fungi in the world.
How to identify it
Cap
The cap is 1.5 to 4 cm across, hemispherical to broadly convex or slightly bell-shaped, rarely expanding fully. Colour is light grey to whitish or very pale tan, often with a faint ochre or brownish tint over the disc when young, drying almost white. The surface is smooth and dry, and in dry weather it commonly cracks into fine areolate patches. Bruised areas darken and take on a blue-green tone.
Gills
Gills are adnate to adnexed, close and moderately broad, pale grey at first and becoming strongly mottled with black patches as spores mature unevenly, finally nearly uniformly black. Gill edges are narrowly white.
Stipe
The stipe is long and slender relative to the cap, 6 to 12 cm tall and only 2 to 4 mm thick, equal or very slightly swollen at the base, hollow and fragile. It is greyish white to pale yellowish, finely pruinose toward the apex and longitudinally lined below, and it stains conspicuously blue to blue-green where handled, with the base often the first part to colour. No ring and no volva are present.
Flesh and spore print
The flesh is thin and whitish and turns blue to blue-green on cutting or bruising, a change that develops over a few minutes and is the single most useful macroscopic character. The spore print is jet-black, and the spores are smooth, thick-walled and lemon-shaped with a broad germ pore.
Where and when it grows
This mottlegill fruits on the dung of cattle, horses and other large herbivores in open pasture, and occasionally on strongly manured ground close to a pat. It grows singly or in small scattered groups directly out of the dung, favouring pats that are a few days to a couple of weeks old and still holding moisture.
It is a species of warm climates, widespread through the tropics and subtropics of the Americas, Africa, Asia, Australia and the Pacific islands, and reaching the warm fringes of Europe and the southern United States. Fruiting is concentrated in the humid rainy season and follows warm downpours, ceasing when pats dry hard.
Ecological role
Panaeolus cyanescens is coprophilous and strictly saprotrophic. It digests the fine plant fibre and nitrogen-rich residues left in herbivore dung, forming no association with living plants and taking its place in the rapid succession of moulds, cup fungi and agarics that colonise a fresh pat.
Dispersal follows the classic dung fungus loop. Black spores are shed onto surrounding pasture, are grazed along with the grass, survive passage through the animal's gut, and germinate in the freshly deposited dung. Because the substrate is ephemeral, the fungus completes its cycle quickly, with mycelium colonising the pat interior and fruit bodies emerging within days of adequate rain.
Similar species
Panaeolus antillarum shares warm pasture dung and a pale cap but is much larger and stouter, with a domed whitish cap up to 8 cm across, and its flesh shows no blue staining. Panaeolus papilionaceus is greyer and bell-shaped with white toothed veil fragments hanging at the cap margin and no bruising reaction. Panaeolus semiovatus is pale but viscid when moist and carries a distinct ring on the stipe.
Among other genera, Deconica coprophila on dung has a viscid chestnut cap with a separable skin and a purple-brown print rather than black, and small Psathyrella species on manured ground are more brittle with paler flaring stipes and no colour change. The combination of a small pale dry cracking cap, a very slender stipe, mottled black gills and prompt blue-green staining where handled is not matched by any of these.