Psilocybe aztecorum is a species of psilocybin mushroom in the family Hymenogastraceae. Known only from central Mexico, the fungus grows on decomposing woody debris and is found in mountainous areas at elevations of 2,000 to 4,000 m (6,600 to 13,100 ft), typically in meadows or open, grassy conifer forests. The mushrooms have convex to bell-shaped caps 1.5–2 cm (0.6–0.8 in) in diameter, atop slender cylindrical stems that are up to 7.5 cm (3.0 in) long. The color of the caps changes with variations in hydration, ranging from dark chestnut brown to straw yellow or whitish when dry. The base of the stem is densely covered with conspicuous white rhizomorphs, a characteristic uncommon amongst Psilocybe species. The species was first reported by French mycologist Roger Heim in 1956 as a variety of Psilocybe mexicana before he officially described it under its current name a year later. Named for its association with the Nahua people also called Aztecs, P. aztecorum may have been one of the sacred mushroom species, or teonanácatl (A Nahuatl word translated variously as "sacred mushroom" or "flesh of the gods"), reported in the codices of 16th-century Spanish chronicler Bernardino de Sahagún. The mushrooms are still used for spiritual ceremonies by Nahua people in the Popocatépetl region, although this traditional usage is waning. The variety P. aztecorum var. bonetii has smaller spores than the main variety, and is found at lower elevations with Montezuma pine (Pinus montezumae) and sacred fir (Abies religiosa). P. aztecorum may be distinguished from similar temperate species such as P. baeocystis and P. quebecensis by their ranges, and by differences in the morphology of microscopic structures like cystidia.
Taxonomy and nomenclature The species was first mentioned by French mycologist Roger Heim in 1956 based on material collected by American ethnomycologist R. Gordon Wasson in Paso de Cortés, on the slopes of Popocatépetl mountain in Mexico. Heim originally named the species as a variety of Psilocybe mexicana; limited to dried mushroom material for analysis, he only described the spores, which he explained were "relatively longer and narrower than that of Psilocybe mexicana". A year later, Heim renamed the fungus Psilocybe aztecorum and officially described it, in addition to several other Mexican Psilocybe taxa. Some of these mushrooms, including P. aztecorum, were illustrated in the popular American weekly magazine Life ("Seeking the Magic Mushroom"), in which Wasson recounted the psychedelic visions that he experienced during the divinatory rituals of the Mazatec people, thereby introducing psilocybin mushrooms to Western popular culture. In 1978, Mexican mycologist and Psilocybe specialist Gastón Guzmán emended the description of P. aztecorum to include the color variation of the cap resulting from its strongly hygrophanous nature, the mycenoid form, the rhizoids at the base of the stem, the lignicolous habitat, and the size of the spores—all features that he thought were either confused, or not sufficiently detailed, in Heim's original description. In the same publication, Guzmán also characterized the variety P. aztecorum var. bonetii, distinguished from the main variety by its smaller spores. He had originally described this variant as a separate species, Psilocybe bonetii, in 1970. Further, Guzmán later published Psilocybe natarajanii, originally described by him from Tamil Nadu in southern India, as a synonym of P. aztecorum var. bonetii; this putative synonymy, however, is confirmed by neither MycoBank nor Index Fungorum. Guzmán called the main variety P. aztecorum var. aztecorum; for this reason, the species authority is often cited as "P. aztecorum var. aztecorum R. Heim emend. Guzmán". Psilocybe aztecorum is the type species of Guzmán's section Aztecorum, a polyphyletic group of bluing (i.e., psilocybin-containing) Psilocybe mushrooms characterized by having a strongly hygrophanous cap that dries to brown or brownish white when dry; spores that appear asymmetrical when seen in side view; and pleurocystidia that, when present, are hyaline (translucent). Other species classified in section Aztecorum are P. baeocystis and P. quebecensis. The specific epithet aztecorum refers to the Aztec peoples of central Mexico, who used this mushroom in traditional ceremonies long before the Spanish came to America. The variety P. aztecorum var. bonneti is named after Dr. Federico Bonet (died 1980), emeritus professor of the Escuela Nacional de Ciencias Biológicas, who assisted Guzmán with his doctoral studies. The popular names of P. aztecorum are niños or niñitos (children or little children), or in the Nahuatl language apipiltzin which means niños del agua ("children of the water"), alluding to their habitat along ravines.
Description
The cap is convex to bell-shaped, sometimes developing a broad umbo before expanding and flattening in age; it reaches a diameter of 1.5–2 cm (0.6–0.8 in). In maturity, the cap eventually forms a central depression, and, in some old specimens, opens into the hollow stem. The cap surface is slimy to the touch, and has translucent striations along the margin when moist. The cap is strongly hygrophanous, meaning that it will change color depending on its level of hydration. The color ranges from yellowish brown to golden yellow in young button forms to brownish gray in age, with greenish-gray tints on the margin. The color later changes to whitish from the center to the margin, finally remaining completely white; dried specimens are straw-colored to pale brownish. In contrast to most psilocybin mushrooms, the cap of P. aztecorum does not have a strong bluing reaction upon injury—only the margin stains slightly green-blue.
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