| Russula emetica | |
|---|---|
 | |
Scientific classification | |
| Kingdom: | Fungi |
| Division: | Basidiomycota |
| Class: | Agaricomycetes |
| Order: | Russulales |
| Family: | Russulaceae |
| Genus: | Russula |
| Species: | R. emetica |
| Binomial name | |
| Russula emetica | |
| Synonyms[5] | |
Russula emetica | |
|---|---|
 | Gills onhymenium |
  | Cap isconvex orflat |
  | Hymenium isadnate orfree |
 | Stipe isbare |
 | Spore print iswhite |
 | Ecology ismycorrhizal |
 | Edibility ispoisonous |
Russula emetica, commonly known asthe sickener,emetic russula, orvomiting russula, is abasidiomycete mushroom, and thetype species of the genusRussula. It was first described in 1774.
It has a red, convex to flatcap up to 8.5 cm (3.3 in) in diameter, with acuticle that can be peeled off almost to the centre. Thegills are white to pale cream, and closely spaced. A smooth whitestem measures up to 10.5 cm (4.1 in) long and 2.4 cm (0.9 in) thick. There are many similar russulas with a red cap and white stem and gills, some of which can be reliably distinguished only by microscopy. The mushroom has a wide distribution in theNorthern Hemisphere, where it grows on the ground in damp woodlands in amycorrhizal association withconifers, especiallypine.
The mushroom'scommon names refer to the gastrointestinal distress which it causes when consumed raw. Theflesh is extremely peppery, but this offensive taste, along with itstoxicity, can be removed byparboiling orpickling. Although it used to be widely eaten in Russia and eastern European countries, it is generally not recommended for consumption.
Russula emetica was first officiallydescribed asAgaricus emeticus byJacob Christian Schaeffer in 1774, in his series on fungi ofBavaria and thePalatinate,Fungorum qui in Bavaria et Palatinatu circa Ratisbonam nascuntur icones.[6]Christian Hendrik Persoon placed it in its current genusRussula in 1796,[7] where it remains. According to the nomenclatural databaseMycoBank,Agaricus russula is asynonym ofR. emetica that was published byGiovanni Antonio Scopoli in 1772, two years earlier than Schaeffer's description. However, this name is unavailable as Persoon's name issanctioned.[8] Additional synonyms includeJean-Baptiste Lamarck'sAmanita rubra (1783), andAugustin Pyramus de Candolle's subsequentnew combinationAgaricus ruber (1805).[5] Thespecific epithet is derived from theAncient Greekemetikos/εμετικος 'emetic' or 'vomit-inducing'.[9] Similarly, itscommon names ofsickener,emetic russula,[10] andvomiting russula also refer to this attribute.[11]
Russula emetica is thetype species of the genusRussula.[12] According toRolf Singer's infragenericclassification ofRussula, it is also the type of thesectionRussula.[13][14] In an alternative classification proposed byHenri Romagnesi, it is the type species of subsectionEmeticinae.[15] Amolecular analysis of EuropeanRussula species determined thatR. emetica groups in aclade withR. raoultii,R. betularum, andR. nana;[16] a later analysis confirmed the closephylogenetic relationship betweenR. emetica and the latter two Russulas.[17]
The stickycap ofR. emetica is 2.5–10 cm (1–4 in) wide, with a shape ranging from convex (in young specimens) to flattened, sometimes with a central depression,[18] and sometimes with a shallowumbo. It is a bright scarlet or cherry red, and in maturity, the margins have fine radial grooves extending 2–7 mm (0.08–0.3 in) towards the center of the cap. Thecuticle can be readily peeled from the cap almost to the centre. The brittleflesh is white (or tinged with red directly under the cap cuticle), measures 4–9 mm (0.2–0.4 in) thick, and has a very sharp and peppery taste. Thegills are closely spaced, white to creamy-white, andadnate toadnexed or completely free. They are intervenose (containing cross-veins in the spaces between the gills) and occasionally forked near the cap margin.[19]
The whitestem measures 4.5–10.5 cm (1.8–4.1 in) long by 0.7–2.4 cm (0.3–0.9 in) thick, and is roughly the same width throughout its length, although it can be a bit thicker near the base. Its surface is dry and smooth, sometimes marked by faint longitudinal grooves. It is either stuffed (filled with a cottony pith) or partially hollow, and lacks aring orpartial veil. The fruit bodies have a slightly fruity or spicy smell.[19]
Russula emetica produces a white to yellowish-whitespore print. Thespores are roughly elliptical to egg-shaped, with a strongly warted and partially reticulate (web-like) surface. They have dimensions of 8.8–11.0 by 6.6–8 μm, and areamyloid, meaning that they willstain blue, bluish-grey, to blackish inMelzer's reagent.Basidia (spore-bearing cells) are club-shaped, four-spored,hyaline (translucent), and measure 32.9–50 by 9.0–11.6 μm.Cystidia located on the gill face (pleurocystidia) are somewhat cylindrical to club-shaped or somewhat spindle-shaped, and measure 35–88 by 7.3–12.4 μm. They are yellowish, and containgranular contents. Cheilocystidia (found on the edges of the gills), which are similar in shape to the pleurocystidia, are thin-walled, hyaline, and measure 14–24 by 4.4–7.3 μm.Clamp connections are absent from thehyphae.[19]
The redpigments of this and other russulas are water-soluble to some degree, and fruit bodies will often bleach or fade with rain or sunlight;[20] the cap colour of older specimens may fade to pink or orange, or develop white blotches.[18] The main pigment responsible for the red colour of the fruit bodies is calledrussularhodin, but little is known of its chemical composition.[21]
Russula emetica is one of over 100 red-cappedRussula species known worldwide.[22] The related beechwood sickener (R. nobilis) is found underbeech in Europe. Many, such as the bloody brittlegill (R. sanguinaria), are inedible; this species can be distinguished fromR. emetica by the reddish flush in its stem.[22] Among the edible lookalikes, there isR. paludosa, commonly found in Europe and North America.R. aurea has a yellow stem, gills and flesh under its red cap.[23] The edibleR. rugulosa—common in mixed woods in the eastern and northern United States—has a wrinkled and pimpled cap cuticle, cream spores, and mild taste.[24] Another inedible species,R. fragilis, has notched gills, and its stem stains blue withnaphthol.[25] The uncommon European subspeciesR. emetica longipes is distinguished by its longer stem and ochre gills.[26] The paler European mushroomR. betularum, found in coniferous forests andmoorland, is sometimes considered a subspecies ofR. emetica.[26]R. nana is restricted in distribution toarctic andsubarctichighland meadows wheredwarf willow (Salix herbacea) oralpine bearberry (Arctostaphylos alpina) are abundant.[27]
_at_Rozendaal_castle_park_-_panoramio.jpg) |  |  |  |  |
| R. paludosa often has a less pronounced cap color | R. sanguinaria has a reddish flush in its stem. | R. nobilis grows in association with beech. | R. aurea has a yellow stem, gills, and flesh. | R. nana grows in highlands with dwarf willow or alpine bearberry. |
Like all species ofRussula,R. emetica ismycorrhizal, and formsmutually beneficial partnerships with roots of trees and certain herbaceous plants. Preferredhost plants areconifers, especiallypines.[22] Fruit bodies grow singly, scattered, or in groups insphagnum moss near bogs, and in coniferous andmixed forests. The fungus occasionally fruits onhumus or on very rotten wood.[19] The mushroom is known from North Africa, Asia and Europe and can be locally very common.[26] There is some doubt over the extent of its range in North America, as some sightings refer to the relatedR. silvicola; initially the name "Russula emetica" was often applied to any red-capped whiteRussula.[19] Sightings in Australia are now referred to the similarly colouredR. persanguinea.[28]
A multi-year field study of the growth ofR. emetica production in ascots pine plantation in Scotland found that total productivity was 0.24–0.49 million mushrooms per hectare per year (roughly 0.1–0.2 million mushrooms/acre/year), corresponding to a fresh weight of 265–460 kg per hectare per year (49–85 lb/acre/year). Productivity was highest from August to October. The longevity of the mushrooms was estimated to be 4–7 days.[29] In a study of the fungaldiversity of ectomycorrhizal species in aSitka spruce forest,R. emetica was one of the top five dominant fungi. Comparing the frequency of fruit body production between 10-, 20-, 30-, or 40-year-old forest stands,R. emetica was most prolific in the latter.[30]
Both thered squirrel (Sciurus vulgaris) and theAmerican red squirrel (Tamiasciurus hudsonicus) are known toforage for, store and eatR. emetica.[31][32] Other creatures that have been documented consuming the mushroom include the snailMesodon thyroidus,[33] several species ofslugs (includingArion ater,A. subfuscus,A. intermedius,Limax maximus,L. cinereoniger, andDeroceras reticulatum),[34] the fruit fliesDrosophila falleni andD. quinaria,[35] and thefungus gnatAllodia bipexa.[36]
As its name implies, the sickener is inedible, though not as dangerous as sometimes described in older mushroom guides.[37] The symptoms are mainly gastrointestinal in nature:nausea,diarrhoea, vomiting, andcolicky abdominal cramps. These symptoms typically begin half an hour to three hours after ingestion of the mushroom,[38] and usually subside spontaneously, or shortly after the ingested material has been expelled from theintestinal tract.[19] The active agents have not been identified but are thought to besesquiterpenes, which have been isolated from the related genusLactarius and fromRussula sardonia.[39] Sesquiterpenoids that have been identified fromR. emetica include the previously known compounds lactarorufin A, furandiol, methoxyfuranalcohol, and an unnamed compound unique to this species.[40]
The bitter taste disappears on cooking and it is said to then beedible, though consumption is not recommended.[25] The mushroom used to be widely eaten in eastern European countries and Russia afterparboiling (which removes the toxins), and then salting orpickling.[22] In some regions of Hungary and Slovakia, the cap cuticle is removed and used as a spice forgoulash.[41]
{{cite book}}:ISBN / Date incompatibility (help)
Media related toRussula emetica at Wikimedia Commons