Panellus stipticus, commonly known as the bitter oyster, the astringent panus, the luminescent panellus, or the stiptic fungus, is a species of fungus in the family Mycenaceae. It is the type species of the genus Panellus. The fungus was given its current scientific name in 1879, but has been known by many names since French mycologist Jean Bulliard first described it as Agaricus stypticus in 1783. Molecular phylogenetic analysis revealed P. stipticus to have a close genetic relationship with members of the genus Mycena. Starting out as tiny white knobs, over a period of one to three months, the mushrooms develop into fan- or kidney-shaped caps that measure up to 3 cm (1.2 in) broad. The caps are orange-yellow to brownish, and attached to the decaying wood by short stubby stalks that are connected off-center or on the side of the caps. Strains from eastern North America are typically bioluminescent, but those from the Pacific coast regions of North America and from other continents are not. The luminescence is localized to the edges of the gills and the junction of the gills with the stem and cap. Bioluminescence is also observable with mycelia grown in laboratory culture, and the growth conditions for optimal light production have been studied in detail. Several chemicals have been isolated and characterized that are believed to be responsible for light production. Genetic analysis has shown that luminescence is controlled by a single dominant allele. A common and widely distributed species, it is found in Eurasia, Australia, and North America, where it grows in groups or dense overlapping clusters on the logs, stumps, and trunks of deciduous trees, especially beech, oak, and birch. Modern research has probed the potential of P. stipticus as a tool in bioremediation, because of its ability to detoxify various environmental pollutants.
Taxonomy
The species was first named Agaricus stypticus by the French botanist Jean Bulliard in 1783, and later sanctioned by Elias Magnus Fries under this name in 1821. Fries later changed the genus as well as the spelling of the epithet and called it Panus stipticus. The species has had an extensive taxonomic history and been shuffled to a number of genera by various authors, resulting in several synonyms: Agaricus flabelliformis (Johann Friedrich Gmelin, 1792), Pocillaria stiptica (Otto Kuntze, 1898), Rhipidium stipticum (Karl Friedrich Wilhelm Wallroth, 1833), Crepidopus stipticus (Samuel Frederick Gray, 1821), Pleurotus stipticus (Paul Kummer), Lentinus stipticus (Joseph Schröter, 1885), and Merulius stipticus (Jean-Baptiste Lamarck). It was Finnish mycologist Petter Karsten who in 1879 assigned its current name. Panellus stypticus is still used in the literature as a variant spelling. Panellus stipticus is the type species of the genus Panellus, and, in Rolf Singer's authoritative 1986 classification of the Agaricales, it is also the type species of subgenus Panellus, an infrageneric (below the taxonomic level of genus) grouping of Panellus species characterized by the absence of cystidia on the sides of the gills. More recently, phylogenetic analyses of the sequences of their ribosomal large subunit genes have concluded that Panellus stipticus is closely related to the poroid mushroom Dictyopanus pusillus. The molecular analysis supports a previous assessment by mycologists Harold Bursdall and Orson K. Miller, who in 1975 suggested merging Dictyopanus into Panellus based on similarities in spore shape, stem structure, and the ability of dried fruit bodies to revive when moistened. Formerly grouped in the family Tricholomataceae, a wastebasket taxon of gilled mushrooms with white spores, P. stipticus is now classified in the Mycenaceae, after a large-scale phylogenetic analysis revealed "a previously unsuspected relationship between Mycena and Panellus (including Dictyopanus)". The fungus is commonly known as the bitter oyster, the luminescent panellus, the astringent panus, or the styptic fungus. The specific epithet stipticus refers to its purported value in stopping bleeding. Etymologically, it is a Greek equivalent to the Latin word astringens, deriving from στυπτικός (styptikós), itself from the verb στύφειν (styphein), "to contract".
Description
The fungus normally exists unseen, in the form of a mass of threadlike vegetative cells called a mycelium, inhabiting rotting wood; only when suitable environmental conditions of temperature, moisture, and nutrient availability are achieved does the fungus produce the reproductive structures known as fruit bodies, or mushrooms. The cap of the fruit body is kidney- or clamshell-shaped, convex to roughly flat, with dimensions of 1.2 to 3.2 cm (0.5 to 1.3 in) by 1.2 to 2.5 cm (0.5 to 1.0 in). The edges of the caps are scalloped with small rounded teeth, and curved slightly inward. The cap surface is dry, with a pattern of block-like areas similar to cracked dried mud; the surface is also covered with small fine hairs that give it a somewhat woolly consistency. It may have several concentric ridges or zones. Fresh fruit bodies range in color from yellowish-orange to buff to cinnamon; when dried they may be various shades of tan, brown or clay. The faded colors of dried fruit bodies tend to revive when moistened. On the underside of the cap, the gills are narrow and spaced closely together, often forked, brownish to buff, and with numerous interconnecting cross-veins. Supporting the cap is a stem that is 0.5 to 2 cm (0.2 to 0.8 in) long by 0.3 to 0.8 cm (0.1 to 0.3 in) thick and has an off-center attachment to the cap, either at or near the cap side. The dull-white stem is covered with minute silk-like fibers and is narrower at the base where it attaches to the substrate. Fruit bodies do not have any distinctive odor. The flesh is thin, tough, and dark yellow-brown to cream-colored.
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