Omphalotus Illudens: The Ultimate Mushroom Guide
About The Omphalotus Illudens Mushroom
Omphalotus Illudens is a large, orange mushroom that is often found in clumps on decaying stumps, buried roots, or at the base of hardwood trees in eastern North America.
It is a common fall mushroom east of the Rocky Mountains, and is frequently found in urban settings, sprouting from and around dead trees and stumps. West of the Rockies, it is very rare, and generally replaced by the very similar Omphalotus olivascens, which is distinguished by the olive shades that are mixed in with the orange.
It's dual claim to fame is that it is a poisonous mushroom whose gills are (weakly) bioluminescent.
Other names: Jack O'Lantern Mushroom.
Omphalotus Illudens Identification
Saprobic; growing in large clusters on the stumps or buried roots of hardwoods, especially oaks; late summer and fall; widely distributed and common east of the Rocky Mountains; very rare in western North America. Also found in northern and central Europe.
3-20 cm; at first convex, with a central bump or point; becoming more or less flat, and eventually shallowly vase-shaped--but usually retaining a small central "nipple"; bald; dry or slightly greasy; bright orange to pumpkin orange; the margin inrolled when young.
Running down the stem; close or crowded; bright orange to pale orange; luminescent when fresh.
3-13 cm long; 1-2 cm thick; tapering to base; solid; bald; pale orange to orange.
Pale orange; unchanging when sliced.
KOH green on cap surface; ammonia greenish on cap surface.
White to creamy or pale yellow.
Hygrophoropsis Aurantiaca has forked gills and does not form caespitose clusters.
Omphalotus Illudens Taxonomy & Etymology
This saprobic mushroom was described in 1822 by American botanist-mycologist Lewis David von Schweinitz (1780 - 1834), who gave it the binomial scientific name Agaricus illudens. The currently accepted scientific name Omphalotus illudens dates from a 1979 publication in Sydowia 8: 106 by mycologists Andreas Bresinsky (born 1935) and Helmut Besl, both of Regensburg University, Germany.
In Britain, this mushroom has been incorrectly referred to as Omphalotus olearius, but that name belongs to a closely-related species that has not been confirmed as occurring in Britain. Valid synonyms of Omphalotus illudens include Agaricus illudens Schwein., and Clitocybe illudens (Schwein.) Sacc.
The genus name Omphalotus means umbilicate (in the form of a navel), and refers to the central depression in mature caps, as seen in the picture above, while the specific epithet illudens means 'deceiving'. Whether the latter is a reference to the fact that many people have been deceived into eating these toxic toadstools in the mistaken belief that they are Chanterelles remains unclear.
Omphalotus Illudens Toxicity
The poisonous chemical compounds illudin S and illudin M were isolated from Omphalotus illudens. In addition to their antibacterial and antifungal effects, illudins appear to be the cause of human toxicity when these mushrooms are eaten raw or cooked. Muscarine has also been indirectly implicated in toxicity, but modern studies to demonstrate its presence in O. illudens are needed.
The cytotoxic effect of illudin is of interest for treating some cancers, but illudin itself is too poisonous to use directly so it must first be chemically modified. Inside human cells, illudin S reacts with DNA and creates a type of DNA damage that blocks transcription. This block can only be relieved by a repair system called nucleotide excision repair. Damage in non-transcribed DNA areas is left unrepaired by the cell. This property was exploited by the company MGI Pharma to develop an illudin-derivative called Irofulven for use as a cancer treatment. Its application is still in the experimental phase.
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