''Cystoderma carcharias'', is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of agaric in the

fungal A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from th ...

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Agaricaceae. It has a widespread distribution, and has been collected in coniferous forests and grasslands in Asia, Europe, North America, and the subantarctic islands. In the field, fruit bodies are characterized by a pink cap up to broad, a well-developed

ring Ring may refer to: * Ring (jewellery), a round band, usually made of metal, worn as ornamental jewelry * To make a sound with a bell, and the sound made by a bell :(hence) to initiate a telephone connection Arts, entertainment and media Film and ...

on the

stem Stem or STEM may refer to: Plant structures * Plant stem, a plant's aboveground axis, made of vascular tissue, off which leaves and flowers hang * Stipe (botany), a stalk to support some other structure * Stipe (mycology), the stem of a mushro ...

, and an unpleasant odour.

Taxonomy

The species was first described scientifically by Christian Hendrik Persoon, who named it ''Agaricus carcharias'' in 1794. Swiss mycologist

Victor Fayod Victor Fayod (23 November 1860 – 28 April 1900) was a Swiss mycologist, who created an influential novel classification of the agaric fungi and who described a number of new genera and species. Biographical overview Fayod was born on 23 Nove ...

assigned it its current name in 1889. The

specific epithet 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, bot ...

''carcharias'' is probably derived from the Greek καρχαρός (''karcharos'') which means sharp, pointed or jagged. καρχαρίας (''karcharias'') is translated as

shark Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimo ...

Description

The fruiting body of ''Cystoderma carcharias'' is a relatively small agaric. The fruiting body is characterised by an off-white and pale pink-tinged cap with a distinct darker central spot, and a powdery cuticle. The cap is at first convex, but with maturity becomes flat and slightly umbonate. The cap is up to in diameter and may bear a margin fringed with remnants of a partial veil. The gills are white, adnate and crowded. The

is white and smooth above, and granular below a white, upturned, flared and persistent

. The

is cylindrical and up to tall. The flesh is white, firm and full throughout. Additionally, ''C. carcharias'' forma ''album'' is a form recognised as having a snow-white cap. Under a microscope, the

spore In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, f ...

s are ellipsoid, with dimensions 4–5.5 by 3–4

µm The micrometre ( international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American spelling), also commonly known as a micron, is a unit of length in the International System of Unit ...

. The spores are white and amyloid. The basidia are 4-spored, club-shaped, and measure 20–25 by 4–6 µm. The fruiting body of ''C. carcharias'' bears a characteristic strong, unpleasant odour. The odour has been described as earthy, muddy and mouldy by various authors. This has been attributed to the presence of the compound

geosmin Geosmin ( ) is an irregular sesquiterpenoid, produced from the universal sesquiterpene precursor farnesyl pyrophosphate (also known as farnesyl diphosphate), in a two-step -dependent reaction. Geosmin, along with the irregular monoterpene 2-met ...

. The taste is not distinctive. ''Cystoderma carcharias'' is a fairly common fungus distributed in Europe, North America and

temperate In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout t ...

Asia, typically occurring in coniferous forests. It has also been found on the treeless, Australian subantarctic Macquarie Island. Fruit bodies are found singly or in groups on soil among grass or moss during late summer and autumn. The fungus is an

acidophilic Acidophiles or acidophilic organisms are those that thrive under highly acidic conditions (usually at pH 5.0 or below). These organisms can be found in different branches of the tree of life, including Archaea, Bacteria,Becker, A.Types of Bacteria ...

litter saprotroph growing frequently under conifers, namely spruce. ''Cystoderma carcharias'' accumulates cadmium in its fruiting bodies. In polluted areas, cadmium concentrations may even exceed 600 mg/kg in dry mass. Intracellular Cd accumulated in sporocarps of ''C. carcharias'' is associated with two isoforms of metallothioneins. Furthermore, ''C. carcharias'' contains numerous organoarsenic compounds from which dimethylarsinoylacetate and trimethylarsoniopropionate have been reported for the first time in the terrestrial environment. This fungus has been deemed inedible by various authors.

References

External links

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Scientific images
at BioImages (UK) {{Taxonbar, from=Q2640662 Agaricaceae Fungi of Europe Fungi of North America Fungi of Asia Fungi of Australia Inedible fungi