What You Should Know
Omphalotus nidiformis is a gilled basidiomycetes mushroom most notable for its bioluminescent (ability for producing light) properties. Its bioluminescence, a blue-green color, is only observable in low light conditions when the eyes get dark-adapted. Not the entire fruit body glows, only the gills do, a phenomenon also called "foxfire". This is due to an enzyme called luciferase, acting upon a compound called luciferin, leading to the emission of light much as fireflies do. Its fruit bodies are generally found growing in overlapping clusters on a wide variety of dead or dying trees. It could be mistaken as an edible pleurotus, but like most glowing mushrooms, the Omphalotus nidiformis is deadly poisonous!
The intensity of the luminescence varies and diminishes with age or if the caps get too wet. The reason for its luminescent is not known, but perhaps it is to attract night-flying insects which feed or forage on it and then spread its spores.
Other names: Ghost Fungus.
Omphalotus nidiformis Mushroom Identification
The fruit bodies of the ghost fungus can be found on dead or diseased wood. They may be first seen at night as a pale whitish glow at the base of trees in a eucalypt forest. The cap is very variable in color, sometimes cream though often tinted with orange, brownish, grayish, purple, or even bluish-black shades. The margin is lighter, generally cream, though brown forms have tan or brown edges. The center generally has several darker shades, and younger specimens are often darker. Growing up to 30 cm (12 in) in diameter it is funnel-shaped or fan-shaped in appearance with inrolled margins.
The cream-white gills are decurrent and often drip with moisture. They are up to 13 mm (0.5 in) deep, somewhat distant to closely spaced, and have a smooth edge until they erode in maturity.
The stem may be central to lateral in its attachment to the cap and is up to 8 cm (3 in) long and tapers to the base.
The thin flesh is generally creamy white but can have reddish tones near the base of the stipe.
Odor and Taste
There is no distinctive smell or taste.
The spores are roughly elliptical, or, less commonly, somewhat spherical, and have dimensions of 7.5–9.5 by 5–7 μm. They are thin-walled, inamyloid, and have a smooth surface. Each features a prominent hilar appendage. The basidia (spore-bearing cells), measuring 32–42 by 6–9 μm, are club-shaped and four-spored, with sterigmata up to 7 μm long. Cheilocystidia (cystidia found on the gill edges) are abundant, and measure 15–40 by 3–6 μm; no pleurocystida (cystidia on the gill faces) are present. The cap cuticle comprises a thin layer of 3–6 μm-wide hyphae that are interwoven either loosely or tightly. All hyphae of O. nidiformis have clamp connections.
Omphalotus nidiformis Toxicity
Its toxicity was first mentioned by Anthony M. Young in his 1982 guidebook Common Australian Fungi. The toxic ingredient of many species of Omphalotus is a sesquiterpene compound known as illudin S. This, along with illudin M and a co-metabolite illudosin, have been identified in O. nidiformis. The two illudins are common to the genus Omphalotus and not found in any other basidiomycete mushroom. An additional three compounds unique to O. nidiformis have been identified and named illudins F, G and H.
Irofulven, a compound derived from illuden S, is undergoing phase II clinical trials as a possible therapy for various types of cancers. Fruit body extracts have antioxidant and free radical scavenging properties, which may be attributed to the presence of phenolic compounds.
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