| Amanita abrupta | |
|---|---|
 | |
| A young specimen | |
Scientific classification | |
| Kingdom: | Fungi |
| Division: | Basidiomycota |
| Class: | Agaricomycetes |
| Order: | Agaricales |
| Family: | Amanitaceae |
| Genus: | Amanita |
| Species: | A. abrupta |
| Binomial name | |
| Amanita abrupta Peck (1897) | |
| Synonyms[3] | |
| |
| Amanita abrupta | |
|---|---|
| Mycological characteristics | |
 | Gills onhymenium |
  | Cap is convex or flat |
 | Hymenium is free |
 | Stipe has aring andvolva |
 | Spore print is white |
 | Ecology ismycorrhizal |
 | Edibility ispoisonous |
Amanita abrupta, commonly known as theAmerican abrupt-bulbed amanita[4] or theAmerican abrupt-bulbed lepidella, is a possibly toxic species offungus in the familyAmanitaceae. Named for the characteristic shape of itsfruit bodies, this whiteAmanita has a slenderstem, acap covered with conical white warts, and an "abruptly enlarged" swollen base. This terrestrial species grows inmixed woods in eastern North America and eastern Asia, where it is thought to exist in amycorrhizal relationship with a variety of bothconiferous anddeciduous tree species.
A. abrupta was firstdescribed by American mycologistCharles Horton Peck in 1897, based on a specimen he found inAuburn, Alabama. Because the remains of thevolva are not present on the bulb in dried, mature, specimens, Peck thought that the species should be grouped withAmanita rubescens andA. spissa.[5]Synonyms include binomials resulting from generic transfers byJean-Edouard Gilbert toLepidella in 1928, and toAspidella in 1940.[3] Both of these genera have since been subsumed intoAmanita.[6]
A. abrupta is thetype species of thesectionLepidella of the genusAmanita, in thesubgenusLepidella, a grouping of relatedAmanita mushrooms characterized by theiramyloidspores.[7] Other North American species in this subgenus includeA. atkinsoniana,A. chlorinosma,A. cokeri,A. daucipes,A. mutabilis,A. onusta,A. pelioma,A. polypyramis,A. ravenelii, andA. rhopalopus.[8] European and Asian species (also in sectionLepidella) that arephylogenetically related—close to it in the evolutionary family tree—includeA. solitaria,A. virgineoides, andA. japonica.[9]
Thespecific epithetabrupta refers to the shape of the swollen base, which is abruptly enlarged rather than gradually tapering.[10] The species'common name is the "American abrupt-bulbed Lepidella".[11]
As with mostmushrooms, the bulk ofA. abrupta lies beneath the ground as an aggregation of fungal cells calledhyphae; under appropriate environmental conditions, the visible reproductive structure (fruit body) is formed. Thecap has a diameter of 4 to 10 centimeters (1+1⁄2 to 4 inches), and has a broadly convex shape when young, but eventually flattens.[11] The central portion of the cap becomes depressed in mature specimens.[11] The cap surface isverrucose—covered with small angular or pyramidal erect warts (1–2 mm tall by 1–2 mm wide at the base);[11] the warts are smaller and more numerous near the margin of the cap,[12] and small fragments of tissue may be hanging from the margin of the cap.[13] The cap surface, the warts, and theflesh are white. The warts can be easily separated from the cap, and in mature specimens they have often completely or partly disappeared.[5] The whitegills are placed moderately close together, reaching the stem but not directly attached to it.
Thestem is6.5 to 12.5 cm (2+1⁄2 to 5 in) tall, and slender, with a diameter of0.5 to 1.5 cm (1⁄4 to1⁄2 in).[10] It is white, smooth (glabrous), solid (that is, not hollow internally), and has an abruptly bulbous base with the shape of a flattened sphere; it may develop longitudinal splits on the sides. The base is often attached to a copious whitemycelium—a visual reminder that the bulk of the organism lies unseen below the surface. Thering is membranous, and persistent—not weathering away with time;[5] the ring may be attached to the stem with white fibers.[12] The mushroom has no distinct odor.[14]
When collected in deposit, such as with aspore print, the spores appear white. Viewed with a microscope, thespores are broadly elliptical or roughly spherical, smooth, thin-walled, and have dimensions of 6.5–9.5 by 5.5 by 8.5 μm. Spores areamyloid (meaning they take upiodine when stained withMelzer's reagent)[15] Thebasidia (spore-bearing cells on the edges of gills) are four-spored and measure 30–50 by 4–11 μm. The bases of the basidia haveclamp connections—short branches connecting one cell to the previous cell to allow passage of the products ofnuclear division. Thecap cuticle comprises a layer of densely interwoven, sightly gelatinized, filamentous hyphae that are 3–8 μm in diameter. The stem tissue is made of sparse, thin, longitudinally oriented hyphae measuring 294 by 39 μm.[16]
The fruit bodies ofAmanita kotohiraensis, a species known only from Japan, bears a superficial resemblance toA. abrupta, butA. kotohiraensis differs in having scattered floccose patches (tufts of soft woolly hairs that are the remains of thevolva) on the cap surface, and pale yellow gills.[17]A. polypyramis fruit bodies have also been noted to be similar toA. abrupta;[14] however, it tends to have larger caps, up to 21 cm (8.3 in) in diameter, a fragile ring that soon withers away, and somewhat larger spores that typically measure 9–14 by 5–10 μm.[18] Theamyloidity and size of the spores are reliable characteristics to help distinguishA. abrupta specimens with less prominently bulbous bases from other lookalike species.[12]
MycologistsTsuguo Hongo and Rokuya Imazeki suggested in the 1980s that the Japanese mushroomA. sphaerobulbosa was synonymous with the North AmericanA. abrupta.[19][20] However, a 1999 study ofAmanita specimens in Japaneseherbaria concluded that they were closely related but distinct species, due to differences in spore shape and in the microstructure of the volval remnants.[21] Another similar species,A. magniverrucata, is differentiated fromA. abrupta by a number of characteristics: the universal veil is clearly separated from the flesh of the cap; the volval warts disappear more quickly because the surface of the capcuticle gelatinizes; the partial veil is more persistent; the spores are smaller and roughly spherical; on the underside of the partial veil, the stem has surface fibrils that are drawn upward so as to somewhat resemble a cortina (a cobweb-like protective covering over the immature spore bearing surfaces);A. magniverrucata has a known distribution limited to the south western coast of North America.[22]
The fruit bodies ofA. abrupta grow on the ground, typically solitary, inmixed conifer anddeciduous forests,[10] usually during autumn.[16] The frequency with which fruit bodies appear depends on several factors, such as season, location, temperature, and rainfall. The mushroom has been described as common in the Southeastern United States;[23] inTexas, it has been called both infrequent,[10] and common in theBig Thicket National Preserve.[24] Like most otherAmanita species,A. abrupta is thought to formmycorrhizal relationships with trees. This is a mutually beneficial relationship where the hyphae of the fungus grow around the roots of trees, enabling the fungus to receive moisture, protection and nutritive byproducts of the tree, and affording the tree greater access to soil nutrients.[25]A. abrupta is widely distributed throughout eastern North America,[10] where it has been found as far north asQuebec, Canada,[26] and as far south asMexico.[27]Orson K. Miller claims to have found it in theDominican Republic where it appeared to be growing in a mycorrizhal association withpine trees.[14] Kuo also mentions a mycorrhizal relationship with bothhardwoods andconifers,[12] while Tulloss lists additional preferred tree hosts such asbeech,birch,fir,tsuga,oak, andpoplar.[11] However,A. abrupta has been shown experimentally to not form mycorrhizae withVirginia Pine.[28]
The mushroom is considered inedible;[29] animal test based studies (mice) with aqueous extracts ofA. abrupta have demonstratedhepatotoxic effects.[30] 2-Amino-4,5-hexadienoic acid is associated with these effects.[31]
