Hygrophorus olivaceoalbus

Hygrophorus olivaceoalbus, commonly known as the olive wax cap, is a species of fungus in the genus Hygrophorus. The fruit bodies (mushrooms) appear from midsummer to late autumn under conifers in North American and Eurasian mountain forests. The mushrooms have olive-brown, slimy caps with dark streaks and a dark umbo; the caps measure 3 to 12 cm (1.2 to 4.7 in) in diameter. Other characteristic features include a slimy stem up to 12 cm (4.7 in) long that is spotted with ragged scales up to a ring-like zone. As its name implies, the mushroom has a waxy cap and gills. It is native to North America and across the northern regions of Europe. According to a publication by the Council of Europe, the fungus is nearly extinct in France.

Hygrophorus olivaceoalbus
Scientific classification
Kingdom:
Fungi
Division:
Basidiomycota
Class:
Agaricomycetes
Order:
Agaricales
Family:
Hygrophoraceae
Genus:
Hygrophorus
Species:
H. olivaceoalbus
Binomial name
Hygrophorus olivaceoalbus
Fr. (Fr.) (1838)
Synonyms[1]

Agaricus adustus Batsch (1783)
Agaricus olivaceoalbus Fr. (1815)
Agaricus limacinus subsp. olivaceoalbus (Fr.) Pers. (1828)
Limacium olivaceoalbum (Fr.) P.Kumm. (1871)

Hygrophorus olivaceoalbus
float
Mycological characteristics
gills on hymenium
cap is umbonate
hymenium is adnate or decurrent
stipe is bare or has a ring
spore print is white
ecology is mycorrhizal
edibility: choice but not recommended

Although Hygrophorus olivaceoalbus is edible, opinions are divided regarding its taste. Besides its usage as an edible mushroom, the fungus possesses antibiotic-like compounds.

Taxonomy and classification

The species was first officially described as Agaricus olivaceoalbus by Elias Fries in 1815.[2] It had earlier been published as Agaricus adustus by August Johann Georg Karl Batsch in 1783,[3] but this was an illegitimate renaming of Agaricus brunneus published in 1774 by Jacob Christian Schäffer.[4][5] It received its current scientific name when Fries transferred it to the genus Hygrophorus in 1838.[6] Paul Kummer moved the species to Limacium in 1871,[7] but this genus has since been sunk into synonymy with Hygrophorus.[8]

Several varieties of H. olivaceoalbus have been proposed:[1][9]

Variety Authority Comments
var. olivaceoalbus (Fr.) Fr. (1883) Nominate taxon
var. candidus Quél. (1881)[10] A form described from the Jura Mountains (France) with fine fibrillose spines at the top of the stem.
var. obesus (Bres.) Rea (1922)[11] Named for its stout stem, this is now synonymous with Hygrophorus latitabundus.[12]
var. intermedius Hesler & A.H.Sm. (1963) Spores react hyaline with potassium hydroxide. It is found under Engelmann spruces in Colorado.
var. gracilis Maire (1933)[13] According to the original description, this variety has smaller spores (9–13 × 6–6.5 μm) than the nominate, and appears in silica-containing soil under pine and beech trees in Spain. Hesler and Smith, however, refer to smaller fruit bodies and larger spores than in the nominate taxon (10–14 × 5.5–7.5 μm); additionally, the hyphae of the cap cuticle react dark brown with Melzer's reagent. According to Hesler and Smith, it occurs under firs in Oregon, Washington, Michigan and British Columbia.[9]

Together with H. pustulatus, H. persoonii, H. mesotephrus and H. latitabundus, H. olivaceoalbus form the section Olivaceoumbrini within the genus Hygrophorus.[14] The fungi of this section have greasy to slimy caps and stems. Their caps are darkish brown grey, olive or orange, and their stems are nattered or somewhat distinctly ringed.[15]

Common names that have been used for the mushroom include the "slimy-sheathed waxy cap", the "olive hygrophorus",[16] the "sheated waxgill"[17] and the "olive wax cap".[18] The specific epithet olivaceoalbus is derived from the Latin words for olive-brown (olivaceus) and white (albus).[11]

Characteristics

Fruit body
Below the ring-like annular zone the stem is nattered; above, it is white and smooth.

The cap of H. olivaceoalbus is 3–12 cm (1.2–4.7 in) wide and is hemispherical in young fungi; they become flatter and wider with age, but they keep their characteristic dark umbo.[9] Underneath the slimy grey to sooty-brown surface, the cap cuticle is streaked with fine, dark grey radially arranged fibers.[17] Young fruit bodies are covered by two velum layers; the inner velum, composed of dark fibrils, becomes a ring or sheath (annular zone) on the stem that is covered by the gelatinous outer layer.[9]

The fruit body has a long stem ranging from 3 to 12 cm (1.2 to 4.7 in), a diameter of 1–3 cm (0.4–1.2 in) and a somewhat slimy surface in wet weather.[19] It is often wavy or bent.[20] The base of the stem is sometimes slimmer than near its apex. Above the annular zone, the stem is smooth and whitish. It is covered by two layers of tissue: the exterior sticky layer, and the comparatively thin interior layer that consists of flaky fibres, similar to those under the cap's slime layer, with which they are initially linked. As the stem grows and increases in length, the interior layer becomes ripped, and breaks up into ragged dark concentric bands. The gills of H. olivaceoalbus are thick, widely spaced and adnate (broadly attached) to decurrent (extending slightly down the stem); they are white (slightly greyish on the base), and have a waxy surface.[19]

The flesh of the mushroom is smooth, thin and white. The taste and odor are mild and have no distinct smell.[21] When treated with a dilute solution of sodium hydroxide (NaOH) or sulfuric acid, the flesh turns reddish. The spore print of H. olivaceoalbus is white.[9]

Microscopic characteristics

The spores are 9–12 × 5–6 µm, ellipsoid, and are not amyloid; their surface is smooth. They are yellow in Melzer's reagent. The basidia have dimension of 46–62 × 7–10 µm, and are tetrasporic with short, stubby sterigmata. They have neither pleurocystidia nor cheilocystidia.[9]

The cap cuticle has a width of 250 to 450 µm and consists of loopshaped, dark hyphae with a width from 2 to 3 µm, which form an ixocutis (a horizontal layer of hyphae embedded in slime) and possess clamp connections; the fungus has no hypocutis. The gill trama consists of hyphae about 3 to 8 µm thick; the cap tissue comprises radial hyphae.[9][21]

The mycorrhiza, formed from H. olivaceoalbus as a fungal partner, such as the Piceirhiza gelatinosa, is white and has a smooth, waxy surface, with several layers of hyphae layered around the tree's roots; sometimes this mycorrhiza shows hypertrophy. The hyphae are covered with a jellylike mass that is secreted from the outer walls of the hyphae.[22][23] The ectomycorrhizae can reach lengths of up to 10 mm (0.39 in) and have few side branches; many older ectomycorrhizae have a cavity at the tip that resembles a hole.[24]

Similar species
Hygrophorus lookalikes
H. latitabundus
H. pustulatus

H. olivaceoalbus shows similarities between other closely related fungi of the genus Hygrophorus, some of which have only minor differences in physical features.[21] Examples include H. pustulatus, H. inocybiformis, H. tephroleucus or H. morrisii. In the field, H. olivaceoalbus is distinguished by a combination of features including the double velum, the dark streaks on the slimy cap, the nattering of the stem, and growth under pines,[20] as well as by microscopic characteristics. There is no risk of confusing it with toxic fungi.[25]

Hygrophorus persoonii and H. olivaceoalbus produce different mycosterine (sterol) and their flesh react differently with the addition of sodium hydroxide (red on H. olivaceoalbus versus olive green on H. persoonii). Furthermore, H. persoonii favours oaks as a mycorrhizal partner.[26] The North American species H. inocybiformis produces a smaller fruit body with caps measuring 3–6 cm (1.2–2.4 in) wide, and dry stems that measure 3–6 cm (1.2–2.4 in) long by 0.5–1.2 cm (0.20–0.47 in) thick.[27]

Ecology and distribution

Hygrophorus olivaceoalbus creates mycorrhizae with conifers. In the West Coast of the United States, associations are most common with Sitka spruces and giant redwoods.[21] In the Rocky Mountains it associates with Engelmann spruce and blue spruce,[19] and in northeast North America with hemlocks.[21] It usually favours acidic and chalky ground with mosses in higher altitudes as well as conifer forests and occasionally mixed forests.[28] The fruit bodies are often found singly, but may also grow in clusters.[17]

The range of H. olivaceoalbus stretches across the northern and western North America[21] as well as across Europe (except the Mediterranean region) and Russia.[28] The fungus typically fruits between late summer and early winter,[19] and occasionally (depending on the geographical location and climate) as early as June or right through December.[9] The population is currently not endangered, except in France, where it is almost extinct.[29]

Importance

Edibility

Hygrophorus olivaceoalbus finds a use especially in the kitchen, but the indistinct taste of the fruit bodies have received a mixed reception overall. Kate Mitchel considers the waxy surface "unappetizing", while David Arora described the taste as "bland and slimy".[19] Some authors suggest removing the cap cuticle before eating.[30][31] Overall, several authors call the mushroom edible, but caution is still required, as "not everyone can eat them".[17] The popularity of this fungus varies from one region to another. It is more commonly consumed in Europe than in North America,[20] and is differently coveted within Europe. For example, in Spain the fungi is more highly appreciated in Catalonia; mushroom dishes in this region are more common than in the rest of Spain.[32]

Cyclopentenonderivate, isolated from H. olivaceoalbus and their semi-synthetic aetylderivate, with R1, R2 and R3 = H or Ac and n = 14 or 16 [14]

Pharmacology

Derivates of cyclopentenones, the so-called hygrophorones, can be obtained from the fruit body of H. olivaceoalbus; the fungus produces them as secondary metabolites. The detected compounds are polyols and have an antifungal and antibacterial effect, especially in connection with Gram-positive bacteria. H. olivaceoalbus is therefore an important source of antibiotics, especially as the hygrophorones also show an effect on bacterial cultures that are resistant against contemporary antibiotics such as methicillin, ciprofloxacin or vancomycin.[33] The fungus has been used in traditional Chinese medicine, where it is known for its curing components, such as 4-, 6- or 4,5,6-tri-O-acetyl hygrophorones B14.[34][35]

References
  1. "Hygrophorus olivaceoalbus (Fr.) Fr. 1838". MycoBank. International Mycological Association. Retrieved February 19, 2011.
  2. Fries, Elias Magnus (1815). Observationes Mycologicae (in Latin). Copenhagen, Denmark: Gerh. Bonnier. p. 5.
  3. Batsch, August Johann Georg Karl (1783). Elenchus fungorum (in Latin and German). Halle an der Saale, Germany: sumptibus E. Mauritii. p. 67.
  4. Schaeffer, Jacob Christian (1774). Fungorum qui in Bavaria et Palatinatu circa Ratisbonam nascuntur Icones (in Latin). 4. Regensburg, Germany: Typis Zunkelianis. p. 16, t.32.
  5. "Agaricus adustus Batsch 1783". MycoBank. International Mycological Association. Retrieved May 31, 2012.
  6. Fries, Elias Magnus (1838). Epicris Systematis Mycologici (in Latin). Uppsala, Sweden: E Typographia Academica. p. 324.
  7. Kummer, Paul (1871). Der Führer in die Pilzkunde (in German). Zerbst, Germany: C. Luppe. p. 119.
  8. Kirk PM, Cannon PF, Minter DW, Stalpers JA (2008). Dictionary of the Fungi (10th ed.). Wallingford, UK: CAB International. p. 383. ISBN 9780851998268.
  9. Hesler, Lexemuel Ray; Smith, Alexander H. (1963). North American species of Hygrophorus. Knoxville, USA: University of Tennessee Press. pp. 291–295.
  10. Quélet, Lucien (1880). "Quelques especes critiques ou nouvelles de la Flore Mycologique de France". Compte Rendu de l'Association Française Pour l'Avancement des Sciences (in French). 9: 661–675 (see p. 667).
  11. Rea, Carleton (1922). British Basidiomycetae: A Handbook to the Larger British Fungi. Cambridge, UK: Cambridge University Press. p. 296.
  12. "Hygrophorus olivaceoalbus var. obesus (Bres.) Rea 1922". MycoBank. International Mycological Association. Retrieved May 31, 2012.
  13. Maire, René. Fungi Catalaunici: Contributions à l'étude de la Flore Mycologique de la Catalogne (PDF). Barcelona, Spain: Museu de Ciencies Naturals. p. 53.
  14. Lübken, Tilo; Schmidt, J; Porzel, A; Arnold, N; Wessjohann, L. (2004). "Hygrophorones A–G: fungicidal cyclopentenones from Hygrophorus species (Basidiomycetes)". Phytochemistry. 65 (8): 1061–1071. doi:10.1016/j.phytochem.2004.01.023. PMID 15110686.
  15. Lübken, Tilo (2006). "Hygrophorone. Neue antifungische Cyclopentenonderivate aus Hygrophorus-Arten (Basidiomycetes)" (PDF) (in German). Halle (Saale), Germany. pp. 27–28.
  16. Laursen, Gary A.; Seppelt, R.D. (2009). Common Interior Alaska Cryptogams: Fungi, Lichenicolous Fungi, Lichenized Fungi, Slime Molds, Mosses, and Liverworts. Alaska, USA: University of Alaska Press. ISBN 978-1-60223-058-3.
  17. Schalkwijk-Barendsen, Helene M.E. (1991). Mushrooms of Western Canada. Edmonton, Canada: Lone Pine Publishing. p. 232. ISBN 978-0-919433-47-2.
  18. Michell, Kate (2006). Field Guide to Mushrooms and Other Fungi of Britain and Europe. London, UK: New Holland Publishers. p. 96. ISBN 978-1-84537-474-7.
  19. Arora, David (1986). Mushrooms Demystified: A Comprehensive Guide to the Fleshy Fungi. Berkeley, USA: Ten Speed Press. pp. 127–128. ISBN 978-0-89815-169-5.
  20. McKnight, Vera B.; Peterson, Roger Tory (1998). A Field Guide to Mushrooms: North America. Boston, USA: Houghton Mifflin Harcourt. p. 208. ISBN 978-0-395-91090-0.
  21. Kuo, Michael (January 2007). "Hygrophorus olivaceoalbus". Mushroomexpert.com. Retrieved May 29, 2012.
  22. Haug, Ingeborg (2002). "Identification of Picea-ectomycorrhizae by comparing DNA-sequences". Mycological Progress. 1 (2): 167–178. doi:10.1007/s11557-006-0016-9. S2CID 35684210.
  23. Norris, J.R.; Read, D.J.; Varma, A.K. (1991). Techniques for the study of mycorrhiza. 23. London, UK: Academic Press. pp. 49 et seq. ISBN 978-0-12-521523-7.
  24. Agerer, Reinhard (2011). "Asexual reproduction of Hygrophorus olivaceoalbus by intracellular microsclerotia in root cells of Picea abies – a winner of ozone stress?". Mycological Progress. 11 (2): 425–434. doi:10.1007/s11557-011-0757-y. S2CID 689597.
  25. Laux, Hans E. (1985). Eßbare Pilze und ihre giftigen Doppelgänger (in German). Stuttgart, Germany: Franckh'sche Verlagshandlung, W. Keller. p. 44.
  26. Lübken, Tilo (2006). "Hygrophorone. Neue antifungische Cyclopentenonderivate aus Hygrophorus-Arten (Basidiomycetes)" (PDF) (in German). Halle (Saale), Germany. pp. 118–119.
  27. Bessette, A.; Miller, O.K. Jr.; Bessette, A.R.; Miller, H.R. (1995). Mushrooms of North America in Color: A Field Guide Companion to Seldom-Illustrated Fungi. Syracuse, USA: Syracuse University Press. p. 48. ISBN 978-0-8156-2666-4.
  28. Jahn, Hermann (1964/65). "Verbreitung und Standorte der Schnecklinge, Hygrophorus, in Westfalen" (PDF). Westfälische Pilzbriefe (in German). 5: 57–67. Check date values in: |year= (help)
  29. Koune, Jean-Paul (2001). Threatened mushrooms in Europe (18th ed.). Council of Europe. p. 52. ISBN 978-92-871-4666-3.
  30. Testi, Antonio (1999). Il Libro dei Funghi d'Italia (in Italian). Giunti Editore. p. 248. ISBN 978-88-440-1405-6.
  31. Houdou, Gérard (2005). Champignons de nos Régions (in French). Romagnat, France: Editions de Borée. p. 115. ISBN 978-2-84494-318-7.
  32. de Román M.; Boa, E. (2004). "Collection, marketing and cultivation of edible fungi in Spain" (PDF). Mycología Aplicada International. 16 (2): 25–33.
  33. Lübken, Tilo (2006). "Hygrophorone. Neue antifungische Cyclopentenonderivate aus Hygrophorus-Arten (Basidiomycetes)" (PDF) (in German). Halle (Saale), Germany: 5. Cite journal requires |journal= (help)
  34. Zhou, Jiaju; Xie, Guirong; Yan, Xinjian (2011). Encyclopedia of Traditional Chinese Medicines – Molecular Structures, Pharmacological Activities, Natural Sources and Applications. 1. Isolated Compounds A–C. Berlin, Germany: Springer. p. 51. ISBN 978-3-642-16734-8.
  35. Zhou, Jiaju; Xie, Guirong; Yan, Xinjian (2011). Encyclopedia of Traditional Chinese Medicines – Molecular Structures, Pharmacological Activities, Natural Sources and Applications. 5. Isolated Compounds T–Z. Berlin, Germany: Springer. p. 149. ISBN 978-3-642-16741-6.
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