Neonothopanus gardneri

Neonothopanus gardneri is a striking bioluminescent mushroom of central and northeastern Brazil, known locally as flor de coco, the coconut flower, because it erupts from the fallen leaf bases of babassu palms. It is one of the largest glowing fungi in the world, with caps that can reach the width of a hand, and the light is bright enough to read shapes by on a moonless night.

The genus Neonothopanus holds a handful of robust, pleurotoid, white-spored species that were once shuffled between Pleurotus, Nothopanus and Lampteromyces. All of the confirmed members glow, and they share a fleshy, off-centre to lateral stipe, deeply decurrent gills and a smooth, dry cap.

What sets N. gardneri apart is the combination of size, its near-exclusive association with babassu palm litter, and the intensity and persistence of the glow, which comes from the gills, cap flesh, stipe and even the mycelium in the substrate.

Cap

Fleshy, 3-12 cm or more across, at first convex with an inrolled margin, soon becoming shallowly funnel-shaped, kidney-shaped or fan-shaped and often lobed or wavy at the edge. The surface is dry, smooth to faintly radially fibrillose, and coloured pale tan, ochre-buff to warm yellowish brown, sometimes paler toward the margin.

Gills

Crowded, narrow and strongly decurrent, running well down the stipe. They are cream to pale yellow-orange by day and are the brightest glowing tissue at night, emitting a steady yellow-green light. Gill edges are even, and short gills of several lengths are interspersed.

Stipe

Off-centre to almost lateral, short and stout, 1-5 cm long, tapering toward the base where it plugs into the palm tissue. It is the same tan colour as the cap or a little paler, dry, solid and firm, without a ring or volva.

Flesh and spore print

Flesh is white to cream, firm and rather tough, and does not change colour appreciably when cut. The spore print is white. Fresh sections of cap flesh and stipe glow faintly, and colonised palm tissue can glow after the mushrooms have gone.

This species is closely tied to the babassu palm (Attalea speciosa) and its relatives, fruiting from the decaying leaf bases, fallen petioles and buried fibrous debris of these palms. It is typical of the cerrado and transitional dry forest and palm groves of central and northeastern Brazil, particularly the states of Tocantins, Piaui, Goias and Maranhao.

Fruiting is concentrated in the wet season, roughly December through March, when night humidity is high. Mushrooms appear in clusters or shelving groups, several to many from a single palm base, and are easiest to find at night when their glow gives them away from many metres off.

Neonothopanus gardneri is a saprophyte and weak parasite of palm tissue, rotting the tough fibrous leaf bases and rachis material that few other fungi attack efficiently. Its mycelium spreads through the palm's decaying vascular tissue and can render whole leaf bases faintly luminous.

The bioluminescence is under circadian control, ramping up after dusk and falling off before dawn. Field observations with artificial glowing models suggest the light draws in beetles, flies, ants and other arthropods, which then carry spores away on their bodies, adding to wind dispersal in the still air of the understorey.

The closely related Neonothopanus nambi is smaller and typically whiter, with a thinner cap and a more distinctly lateral or absent stipe, and it grows on woody debris rather than palm leaf bases. Omphalotus species, the jack-o'-lanterns, also glow and have decurrent gills but are bright orange throughout with sharper, more blade-like gill edges and a more central stipe when growing on stumps.

Non-glowing Pleurotus species that share the shelving habit have a smoother, greyer or creamier cap, softer flesh and gills that are broader and less crowded. Lentinus species growing on palm debris can be told by their tough, often scaly caps and serrated gill edges, and none of them produce light.