Psilocybe

Psilocybe is a genus of gilled mushrooms growing worldwide. This genus is best known for the species with psychedelic properties. Psilocybin, psilocin and baeocystin are the main psychedelic compounds responsible for the psychoactive effects of many species in the genus. The word Psilocybe comes from the Greek words ψιλός + κύβη, and literally means 'bare headed', referring to the mushroom's detachable pellicle (loose skin over the cap). It is pronounced with the primary stress on the third syllable, /ˌsaɪloʊˈsaɪbi/ SY-loh-SY-bee. The final e is not silent. Psilocybe fruit bodies are typically small, nondescript mushrooms with a typical 'little brown mushroom' morphology. Macroscopically, they are characterized by their small to occasionally medium size, brown to yellow-brown coloration, with a typically hygrophanous cap, and a spore print-color that ranges from lilac-brown to dark purple-brown (though rusty-brown colored varieties are known in at least one species). Hallucinogenic species typically have a blue-staining reaction when the fruit body is bruised. Microscopically, they are characterized by pileipellis with hyphae that run parallel to the pileus surface, forming a cutis, by their lack of chrysocystidia, and by spores that are smooth, ellipsoid to rhomboid to subhexagonal in shape, with a distinct apical germ pore. Ecologically, all species of Psilocybe are saprotrophs, growing on various kinds of decaying organic matter. A 2002 study of the molecular phylogeny of the agarics indicated that the genus Psilocybe as then defined was polyphyletic, falling into two distinct clades that are not directly related to each other. The blue-staining hallucinogenic species constituted one clade and the non-bluing species the other. The previous type species (Psilocybe montana) of the genus was in the non-bluing clade, but in 2010 the type species was changed to Psilocybe semilanceata, a member of the bluing clade. A 2006 molecular phylogenetic study of the Agaricales by Matheny and colleagues, further demonstrated the separation of the bluing and non-bluing clades of Psilocybe in a larger, strongly supported phylogenetic tree of the Agaricales. Psilocybe had been placed taxonomically in the agaric family Strophariaceae based upon its spore and pileipellis morphology. The phylogenetic study by Matheny et al., placed the non-bluing Psilocybe and its close relatives in a basal position within the Strophariaceae, a sister taxon to a clade containing the other genera within that family. The bluing Psilocybe, however, form a clade that is sister to Galerina in the newly revised family, Hymenogastraceae that used to be restricted to secotioid, false-truffles. The phylogenetic study by Moncalvo, et al. confirmed that the agaric genus Melanotus is simply a subgroup of the non-bluing Psilocybe, all of which are placed in Deconica, and also pointed to a close relationship between the latter genus and the genera Kuehneromyces and Phaeogalera. In 2007, a paper by Redhead et al. proposed conserving the genus Psilocybe with Psilocybe semilanceata as its type species. The suggestion was accepted by unanimous vote of the Nomenclature Committee for Fungi of the International Botanical Congress in 2010, meaning that P. semilanceata (a member of the bluing clade) now serves as the type species of the genus. Since P. semilanceata is now the type species of the genus, the bluing hallucinogenic clade remained in the genus Psilocybe (Hymenogastraceae) while the non-bluing clade were transferred to the genus Deconica (Strophariaceae). However, it has been demonstrated that Psilocybe fuscofulva, a species that used to be known as Psilocybe atrobrunnea, belongs to the genus Psilocybe s.s. but does not contain psychotropic compounds. Geographically, species in this genus are found throughout the world in most biomes. The greatest species diversity seems to be in the neotropics, from Mesoamerica through Brazil and Chile. Psilocybe are found in a variety of habitats and substrates. Many of the species found in temperate regions, such as Psilocybe cyanescens, seem to have an affinity for landscaped areas mulched with woodchips and are actually rather rare in natural settings removed from human habitation. Contrary to popular belief, only a minority of Psilocybe species, such as P. cubensis and P. subcubensis, grow directly on feces. Many other species are found in habitats such as mossy, grassy, or forest humus soils. The psilocybin molecule is indirectly responsible for the hallucinogenic properties of the Psilocybe. This compound, as well as all other indole alkaloids, are derived from the amino acid tryptophan, being the only amino acid with the indole-amine ring. Tryptophan is converted to tryptamine by decarboxylation. Two methylation steps occur producing DMT, another psychedelic compound. Hydroxylation of this compound produces the more potent hallucinogen psilocin, followed by phosphorylation yielding psilocybin. After ingestion of the psilocybin compound alkaline phosphatases present in the body's digestive system, kidneys, and possibly in the blood readily cleave the phosphoryl ester bond from psilocybin, yielding the hydroxyl compound, psilocin. Psilocin is the chemical primarily responsible for the hallucinogenic effects of the Psilocybe. The blue-staining species of Psilocybe are characterized by the presence of psilocin and psilocybin. This blue-staining reaction occurs after the fruit body has been injured, particularly near the base of the stalk. This reaction is thought to be due to the oxidation of psilocybin after the outer surface of the fruit body has been breached. The degree of bluing in a Psilocybe fruit body roughly correlates with the concentration of psilocin in the mushroom. Psilocybin is chemically far more stable than psilocin, the latter compound being largely lost when the mushroom is heated or dried.