Boletus torosus

Boletus torosus
Scientific classification
Kingdom: Fungi
Division: Basidiomycota
Class: Agaricomycetes
Order: Boletales
Family: Boletaceae
Genus: Boletus
Species: B. torosus
Binomial name
Boletus torosus
Fr. & Hök (1835)
Synonyms[1][2]
  • Dictyopus torosus (Fr.) Quél. (1886)
  • Boletus purpureus var. xanthocyaneus Romagn. (1948)
  • Boletus xanthocyaneus (Ramain) Romagn. (1976)
Boletus torosus
View the Mycomorphbox template that generates the following list

Mycological characteristics

pores on hymenium

cap is convex

or flat
stipe is bare
spore print is olive-brown
ecology is mycorrhizal
edibility: poisonous

Boletus torosus, commonly known as the brawny bolete, is a species of bolete fungus in the family Boletaceae. It is native to southern Europe east to the Caucasus, and Israel. It is generally associated with deciduous trees such as hornbeam, oak and beech in warm dry locales, and is generally rare in Europe. It appears to be relatively common in Hungary. Appearing in summer and autumn on chalky soils, the stocky fruit bodies have an ochre cap up to 20 cm (8 in) across, yellow pores, and a wine-red to brown or blackish stipe up to 6–15 cm (2.4–5.9 in) long by 3–6 cm (1.2–2.4 in) wide. The pale yellow flesh changes to different colours when broken or bruised depending on age, younger mushrooms reddish and older ones with bluish changes as well.

Elias Magnus Fries and Christopher Theodor Hök first described Boletus torosus in 1835. Modern molecular phylogenetics shows that it is only distantly related to the type species of Boletus and will most likely be placed in a new genus pending further study. Eating this species raw leads to vomiting and diarrhea. Gastrointestinal symptoms have also occurred after eating cooked specimens, though some people have eaten it without ill-effects.

Taxonomy

Elias Magnus Fries and Christopher Theodor Hök described this species in 1835, and noted it grew under beech in Switzerland.[3] Lucien Quélet's transferred the species to the now obsolete genus Dictyopus in 1886, which resulted in the synonym Dictyopus torosus.[4] According to Italian mycologist Carlo Luciano Alessio,[1] additional synonyms include Henri Romagnesi's 1948 Boletus purpureus var. xanthocyaneus, and the same taxon, promoted by Romagnesi to distinct species status in 1976,[5] Boletus xanthocyaneus; others, however, consider B. xanthocyaneus a distinct species.[6][7][8] The specific epithet torosus, which derives from Latin, means "muscular".[9] In the United Kingdom, it is known commonly as the "brawny bolete".[10] The German name Ochsen-Röhrling means "oxen bolete".[11]

Boletus torosus is classified in Boletus section Luridi,[12] which includes species producing medium to large fruit bodies with thick, swollen stipes, and minute pores.[13] In a molecular analysis of Boletaceae phylogeny, Boletus torosus was most closely related to B. luteocupreus; these two species formed a clade that was sister to B. luridus.[14] Genetic analysis published in 2013 shows that B. torosus and many (but not all) red-pored boletes are part of a dupainii clade (named for Boletus dupainii), well-removed from the core group of Boletus edulis and relatives within the Boletineae. This indicates that it will most likely be placed in a new genus.[15]

Description

The base of the thick stipe is wine-red coloured.

Quite heavy compared with other mushrooms of similar size, the stocky fruit body contains relatively high amounts of chitin. It has been described as, "having a stone in your hand".[16] The cap is 6–20 cm (2.4–7.9 in) in diameter. Hemispherical when young, it extends and flattens into a convex and finally a flattish shape, sometimes forming a slight depression in the centre. The cap margin is initially curled downward and inward, and gradually turns outward, eventually flattening in maturity, and sometimes protruding beyond the tubes. The surface texture starts out slightly velvety, but becomes smoother and hairless with age; in moist weather, the cap is slightly sticky. The colour of the cap changes over time: initially vivid yellow or golden yellow, then ochre, then darkening in age to brown. However, if the cap cuticle is bruised, or even touched, there are sudden changes in the colour that depend on the age of the mushroom: young, yellow cap becomes cherry-red, while ochre-brown cap tissue bruises to reddish-purple. These colour changes soon give way to bluish or greyish tones, which, when combined, give the cap a variegated appearance. The sulfur-yellow colour of the pore surface on the cap underside becomes less intense with age. The squat stipe measures 6–15 cm (2.4–5.9 in) long by 3–6 cm (1.2–2.4 in) thick. Egg-shaped when young, it lengthens somewhat as the mushroom grows, but is still bulbous in maturity; a mature stipe is typically a little shorter than the diameter of the cap. It is initially roughly the same colour as the cap, but as it matures, develops a wine-red colouration near the base and a sordid-brown to bluish-black colouration elsewhere. The surface has a mesh-like pattern (reticulation) that has a colour development similar to that of the cap: initially yellow, then purplish, and finally dark brown. The flesh is thick and hard. It is yellow, except for the stipe base where it is deep red, or dark brownish in older mushrooms. The pores, stipe and flesh turn greenish-blue with bruising or cutting.[1] The smell is unpleasant, but the taste is mild.[17]

The spore print is olive-brown. The smooth oval spores measure 12–15 by 5–6 μm, and sometimes have an internal oil drop. The basidia (spore-bearing cells) are club-shaped, four-spored, and measure 22–34 by 8–9 μm. The fusiform (fuse-shaped) cystidia are colourless with oil droplets, and have dimensions of 40–50 by 7–8 μm.[1]

Several chemical tests can be used to distinguish B. torosus from other similar Luridi species, such as B. rhodopurpureus and B. xanthopurpureus. B. torosus displays the following characteristic colour changes with tests performed on cut flesh less than 12 hours old: ammonium hydroxide (NH4OH)–yellow centre bordered by a blue circular outer ring; potassium hydroxide (KOH)– deep buff (instantly); ferrous sulphate (FeS04)–no change; Melzer's reagent–dark blue; phenol–blue green (very slow); formalin–mid blue (slow).[7]

Toxicity

Like many boletes, Boletus torosus causes gastrointestinal symptoms such as abdominal pain, diarrhea and vomiting when eaten raw. This can also happen to some people when eaten cooked, though others have consumed it with no ill effects.[16] In a 1994 study, researchers Ulrich Kiwitt and Hartmut Laatsch looked for antabuse-like compound coprine content in Boletus luridus, which had been suspected of inducing antabuse-like reactions with alcohol, and similar species.[18] Coprine ingestion results in heat and flushing in the face, tingling in arms and legs, nausea and vomiting, and tachycardia within five to ten minutes of consuming alcohol.[19] They found none in the suspect species, but did find indications for it in Boletus torosus. They concluded that the most likely explanation for historical incidents was a misidentification of B. torosus with B. luridus, though they could not rule out B. luridus containing a hitherto unidentified compound causing alcohol-related reactions.[18] No clinical cases of alcohol-related sensitivity have been recorded for B. torosus.[16]

Habitat and distribution

Boletus torosus is native to southern Europe east to the Caucasus,[17] and Israel.[12] It is generally associated with deciduous trees such as Carpinus, Quercus and Fagus in warm dry locales, and is generally rare in Europe. In the United Kingdom, it is listed as a "priority species"—a threatened species requiring conservation action under the UK Biodiversity Action Plan.[20] It appears to be relatively common in Hungary.[21] It is found under Palestine oak (Quercus calliprinos) in the Bar'am forest in Upper Galilee.[12] Fruitings typically occur from July to September in calcareous (chalky) soil, either singly or in small groups.[1]

See also

List of Boletus species

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 Alessio CL. (1985). Boletus Dill. ex. L. Fungi Europaei (in Italian) 2. Saronno, Italy: Biella Giovanna. p. 226–27.
  2. ↑ "Boletus torosus Fr. & Hök: 10, 1835". MycoBank. International Mycological Association. Retrieved 2013-03-22.
  3. ↑ Fries EM, Hök CT. (1835). Boleti, fungorum generis illustratio (in Latin). Uppsala, Sweden: Regiae Academiae Typographia. p. 10.
  4. ↑ Quélet L. (1886). Enchiridion Fungorum in Europa media et praesertim in Gallia Vigentium (in French). Lutetia: Octave Dion. p. 160.
  5. ↑ Romagnesi H. (1976). "Nomenclature des bolets du groupe Purpureus Pers. ex Mich. ss. Fries". Bulletin de la Société Mycologique de France (in French) 92 (3): 305–10.
  6. ↑ Brillouet J-M, Brillouet T. (1993). "Descrizione comparativa di raccolte di Boletus xanthocyaneus Ramain ex Romagnesi e di Boletus torosus Fries". Rivista di Micologia (in Italian) 36 (1): 65–72.
  7. ↑ 7.0 7.1 Hills A. (1997). "Notes on the British species of the Boletus torosus complex". Mycologist 11 (4): 159–64. doi:10.1016/S0269-915X(97)80092-4.
  8. ↑ Estadès A, Deïana JC. (2004). "Boletus xanthocyaneus et Boletus torosus. Deux espèces distinctes". Bulletin Mycologique et Botanique Dauphiné-Savoie (in French) 127: 15–30.
  9. ↑ Gledhill D. (2008). The Names of Plants. Cambridge University Press. p. 382. ISBN 978-0-521-86645-3.
  10. ↑ "Recommended English Names for Fungi in the UK" (PDF). British Mycological Society.
  11. ↑ Michael E, Kreisel H. (1983). Handbuch für Pilzfreunde. 1. Die wichtigsten und häufigsten Pilze mit besonderer Berücksichtigung der Giftpilze (in German). G. Fischer. p. 338. ISBN 978-3-437-30436-1.
  12. ↑ 12.0 12.1 12.2 Avizohar-Hershenzon Z, Binyamini N. (1972). "Boletaceae of Israel: I. Boletus sect. Luridi". Transactions of the British Mycological Society 59 (1): 25–30. doi:10.1016/s0007-1536(72)80037-8.
  13. ↑ Snell W, Dick EA. (1970). The Boleti of Northeastern North America. Lehre, Germany: J. Cramer. p. 79. ISBN 978-0-85486-016-6.
  14. ↑ Halling RE, Baroni TJ, Binder M. (2007). "A new genus of Boletaceae from eastern North America". Mycologia 99 (2): 310–16. doi:10.3852/mycologia.99.2.310. PMID 17682784.
  15. ↑ Nuhn ME, Binder M, Taylor AFS, Halling RE, Hibbett DS. (2013). "Phylogenetic overview of the Boletineae". Fungal Biology 117 (7–8): 479–511. doi:10.1016/j.funbio.2013.04.008. PMID 23931115.
  16. ↑ 16.0 16.1 16.2 Flammer R. (2008). "Boletus torosus – Coprin und Alkohol". Schweizerische Zeitschrift für Pilzkunde 2008 (4): 146–47.
  17. ↑ 17.0 17.1 Assyov B. (2013). "Boletus torosus". boletales.com. Retrieved 2013-08-17.
  18. ↑ 18.0 18.1 Kiwitt U, Laatsch H. (1994). "Coprin in Boletus torosus: Beruht die angebliche Alkoholunverträglichkeit durch den Verzehr des Netzstieligen Hexenröhrlings (Boletus luridus) auf einer Verwechslung?" [Coprine in Boletus torosus: Is the alleged alcohol hypersensitivity by ingestion of B. luridus caused by a mistake?] (PDF). Zeitschrift für Mykologie (in German) 60 (2): 423–30.
  19. ↑ Benjamin DR (1995). Mushrooms: poisons and panaceas—a handbook for naturalists, mycologists and physicians. New York: WH Freeman and Company. pp. 288–89. ISBN 0-7167-2600-9.
  20. ↑ Joint Nature Conservation Committee (15 December 2010). UK priority species pages – Version 2. Boletus torosus Fr. & Hök (Report).
  21. ↑ Benedek L, Pál-Fám F. (2006). "Rare macrofungi from Central Börzsöny I. Hungarian occurrence data and habitat preference". International Journal of Horticultural Science 12 (1): 45–52. ISSN 1585-0404.

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