''Tapinella atrotomentosa'', commonly known as the velvet roll-rim or velvet-footed pax, is a species of fungus in the family

Tapinellaceae The Tapinellaceae are a family of fungi in the order Boletales. Members of this family are: ''Bondarcevomyces'', ''Pseudomerulius ''Pseudomerulius'' is a genus of fungi in the Tapinellaceae The Tapinellaceae are a family of fungi in the ord ...

. Although it has

gills A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

, it is a member of the pored mushroom order

Boletales The Boletales are an order of Agaricomycetes containing over 1300 species with a diverse array of fruiting body types. The boletes are the best known members of this group, and until recently, the Boletales were thought to only contain boletes ...

. August Batsch described the species in 1783. It has been recorded from Asia, Central America, Europe and North America. Tough and inedible, it grows on tree stumps of

conifer Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single extant class, Pinopsida. All ex ...

s. The mushroom contains several compounds that act as deterrents of feeding by insects.

Taxonomy

''Tapinella atrotomentosa'' was originally described as ''Agaricus atrotomentosus'' by German naturalist August Batsch in his 1783 work ''Elenchus Fungorum'', and given its current name by Josef Šutara in 1992. It is commonly known as the "velvet-footed pax", and the "velvet rollrim". Historical

synonyms A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are ...

include ''Paxillus atrotomentosus'' by Elias Magnus Fries (1833), ''Rhymovis atrotomentosa'' by Gottlob Ludwig Rabenhorst (1844), and ''Sarcopaxillus atrotomentosus'' by Ivan Zmitrovich (2004). The

variety Variety may refer to: Arts and entertainment Entertainment formats * Variety (radio) * Variety show, in theater and television Films * ''Variety'' (1925 film), a German silent film directed by Ewald Andre Dupont * ''Variety'' (1935 film), ...

''bambusinus'' was described from Trinidad in 1951 by British mycologists Richard Eric Defoe Baker and William Thomas Dale. The

species name In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bo ...

is derived from the

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power ...

words ''atrotomentosus'', meaning "black-haired". It is still commonly seen under its old name ''Paxillus atrotomentosus'' in guidebooks. ''Tapinella atrotomentosa'' and its relative '' T. panuoides'' were placed in a separate genus '' Tapinella'' on account of their habit of growing on (and rotting) wood, and microscopic differences including much smaller spore size, lack of cystidia, and differing

basidia A basidium () is a microscopic sporangium (a spore-producing structure) found on the hymenophore of fruiting bodies of basidiomycete fungi which are also called tertiary mycelium, developed from secondary mycelium. Tertiary mycelium is highly- ...

. Their off-centre stipe also distinguished them from other members of the genus ''

Paxillus ''Paxillus'' is a genus of mushrooms of which most are known to be poisonous or inedible. Species include '' Paxillus involutus'' and ''Paxillus vernalis''. Two former species—'' Tapinella panuoides'' and '' Tapinella atrotomentosa''—have ...

'', and genetic analysis confirmed them as only distantly related.

Description

The fruit body is squat mushroom with a

cap A cap is a flat headgear, usually with a visor. Caps have crowns that fit very close to the head. They made their first appearance as early as 3200 BC. Caps typically have a visor, or no brim at all. They are popular in casual and informal se ...

up to across, sepia- or walnut brown in colour with a rolled rim and depressed centre. The stem is covered with dark brown or black velvety fur. The

are cream-yellow and forked, while the thick stipe is dark brown and juts out sidewards from the mushroom. The flesh is yellowish, and has been described as appetising in appearance, and is little affected by insects; the taste however is acrid. The

spore print 300px, Making a spore print of the mushroom ''Volvariella volvacea'' shown in composite: (photo lower half) mushroom cap laid on white and dark paper; (photo upper half) cap removed after 24 hours showing pinkish-tan spore print. A 3.5-centimeter ...

is yellow and the spores are round to oval and measure 5-6 μm long.

Distribution and habitat

It is a

saprobic Saprotrophic nutrition or lysotrophic nutrition is a process of chemoheterotrophic extracellular digestion involved in the processing of decayed (dead or waste) organic matter. It occurs in saprotrophs, and is most often associated with fungi ( ...

fungus found growing on tree stumps of

s in North America, Europe, Central America (Costa Rica), east into Asia where it has been recorded from Pakistan and China. The fruit bodies appear in summer and autumn, even in drier spells when other mushrooms are not evident.

Toxicity

The species contains toxins which may cause gastrointestinal upset. There have been cases of poisoning reported in European literature. Although ''Tapinella atrotomentosa'' mushrooms are not generally considered edible, they have been used as a food source in parts of eastern Europe. Tests on the chemical composition and free

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha ...

levels of the mushroom suggest that they are not considerably different from other edible gilled mushrooms such as ''

Armillaria mellea ''Armillaria mellea'', commonly known as honey fungus, is a basidiomycete fungus in the genus '' Armillaria''. It is a plant pathogen and part of a cryptic species complex of closely related and morphologically similar species. It causes Arm ...

''. Linus Zeitlmayr reports that young mushrooms are edible, but warns than older ones have a foul bitter or inky flavour and are possibly poisonous. The bitter flavour is allegedly improved by boiling the mushrooms and discarding the water, but is indigestible to many.

Chemistry

''Tapinella atrotomentosa'' has a wound-activated

defence mechanism In psychoanalytic theory, a defence mechanism (American English: defense mechanism), is an unconscious psychological operation that functions to protect a person from anxiety-producing thoughts and feelings related to internal conflicts and o ...

whereby injured fruit bodies convert chemicals known as leucomentins into atromentin,

butenolide Butenolides are a class of lactones with a four-carbon heterocyclic ring structure.Joule JA, Mills K. (2000). Heterocyclic Chemistry 4th ed. Blackwell Science Publishing: Oxford, UK They are sometimes considered oxidized derivatives of furan. Th ...

, and the feeding deterrent osmundalactone. Atromentin had previously been identified as the

pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic comp ...

producing the brown colour of the cap, but was not characterized as a chemical defence compound until 1989. Other compounds produced by the fungus include the orange-yellow flavomentins and violet spiromentin pigments. A novel dimeric

lactone Lactones are cyclic carboxylic esters, containing a 1-oxacycloalkan-2-one structure (), or analogues having unsaturation or heteroatoms replacing one or more carbon atoms of the ring. Lactones are formed by intramolecular esterification of the co ...

, bis-osumundalactone, was isolated from the variety ''bambusinus''. Several phytoecdysteroids (compounds related to the insect moulting hormone

ecdysteroid Ecdysteroids are arthropod steroid hormones that are mainly responsible for molting, development and, to a lesser extent, reproduction; examples of ecdysteroids include ecdysone, ecdysterone, turkesterone and 2-deoxyecdysone. These compounds ...

) have been identified from the fungus, including paxillosterone, 20,22-''p''-hydroxybenzylidene acetal, atrotosterones A, B, and C, and 25-hydroxyatrotosterones A and B.

References

External links

{{Taxonbar, from=Q1415446 Boletales Fungi of Asia Fungi of Central America Fungi of Europe Fungi of North America Inedible fungi Fungi described in 1783 Taxa named by August Batsch