Panaeolus antillarum

Panaeolus antillarum is one of the largest and palest members of its genus, a robust dung-inhabiting agaric of tropical, subtropical and warm-temperate regions. It has often been recorded under the name Panaeolus phalaenarum, and the two are widely treated as the same fungus.

Where most mottlegills are small and dingy grey-brown, this species can reach 6 cm or more across with a clean whitish to pale cream cap that stands out conspicuously on a cow pat. That pallor, combined with the standard Panaeolus characters of mottled gills and a jet-black spore print, makes it one of the more readily recognised species in the group.

It is a classic dung specialist, following grazing cattle and water buffalo through the warm regions of the world and fruiting abundantly in the rainy season.

Cap

The cap is 3 to 8 cm across, at first egg-shaped or hemispherical and expanding to broadly convex, retaining a domed profile rather than flattening. The surface is smooth, dry to slightly tacky, and whitish, cream or very pale grey-buff, sometimes with an ochre tint over the disc. In dry sunny weather the skin frequently cracks into shallow areolate patches, and the margin may be hung with a few thin whitish veil remnants when young.

Gills

Gills are adnexed to adnate, crowded and broad, changing from pale grey through strongly mottled greyish black to virtually black at maturity. The mottling is pronounced in this species, giving a marbled appearance, and gill edges are narrowly white and finely fringed.

Stipe

The stipe is stout for the genus, 6 to 15 cm long and 3 to 8 mm thick, more or less equal or slightly thickened at the base, hollow, firm and whitish to pale grey, often becoming dingy brownish with age or handling. The surface is finely lined or pruinose above and may be minutely scurfy below. No ring and no volva are present.

Flesh and spore print

The flesh is whitish, thin in the cap but firmer in the stipe than in most mottlegills, and shows no distinct colour change when cut. The spore print is jet-black; the spores are smooth, thick-walled, lemon-shaped and have a broad germ pore.

This fungus is a dung specialist, fruiting on the dung of cattle and water buffalo, and less often horses, in open pasture, paddock and grazing land. It grows directly out of the pat, usually singly or in small groups of a few fruit bodies, and can be spectacular when a whole field of pats flushes at once after rain.

It is a species of warm climates, common through the Caribbean, Central and South America, tropical Africa, South and Southeast Asia, Australia and the Pacific, and reaching the warmer parts of southern Europe and the southern United States. Fruiting follows the rains and is concentrated in the hot humid months, when pats stay moist long enough for the fungus to complete its cycle.

Panaeolus antillarum is coprophilous and strictly saprotrophic, digesting the partly broken-down plant fibre in herbivore dung. It arrives in the pat as spores that have already passed through the animal's digestive tract, germinating once the dung is deposited and competing with the fast-moving succession of moulds, dung cups and other coprophilous fungi.

The life cycle is timed to the drying of the pat. Mycelium colonises the moist interior quickly, and fruit bodies push through the crust within days of suitable rain, releasing black spores onto surrounding herbage where they wait to be grazed again. This coprophilous loop ties the species tightly to the presence of large grazing mammals, which is why its global spread has broadly followed cattle and buffalo husbandry.

The nearest relative in the same habitat is Panaeolus papilionaceus, which is smaller, greyer and distinctly bell-shaped, with white toothed veil fragments dangling from the cap margin; this species is far paler, larger and domed with a mostly clean margin. Panaeolus cinctulus is reddish-brown with a dark drying band and prefers compost to raw dung.

Panaeolus semiovatus is the closest match in size and pale colour, but it is markedly viscid when moist and carries a distinct membranous ring on the stipe, a structure entirely absent in P. antillarum. Pale Agaricus species can occur in the same pastures but have free gills passing through pink to chocolate brown, a ringed stipe and a dark brown rather than black print, and Volvopluteus or Volvariella species growing on rich ground have a sac-like volva at the stipe base and a pink spore print.