| Hydnum repandum | |
|---|---|
 | |
Scientific classification | |
| Kingdom: | Fungi |
| Division: | Basidiomycota |
| Class: | Agaricomycetes |
| Order: | Cantharellales |
| Family: | Hydnaceae |
| Genus: | Hydnum |
| Species: | H. repandum |
| Binomial name | |
| Hydnum repandum | |
| Synonyms[6] | |
| Hydnum repandum | |
|---|---|
| Mycological characteristics | |
 | Teeth onhymenium |
 | Cap is depressed |
 | Hymenium is decurrent |
 | Stipe is bare |
 | Spore print is white to cream |
 | Ecology ismycorrhizal |
 | Edibility ischoice |
Hydnum repandum, commonly known as thesweet tooth,pig's trotter,[7]wood hedgehog orhedgehog mushroom, is abasidiomycete fungus of the familyHydnaceae. Firstdescribed byCarl Linnaeus in 1753, it is thetype species of the genusHydnum.
The fungus producesfruit bodies (mushrooms) that are characterized by theirspore-bearing structures—in the form of spines rather thangills—which hang down from the underside of thecap. The cap is dry, colored yellow to light orange to brown, and often develops an irregular shape, especially when it has grown closely crowded with adjacent fruit bodies. Themushroom tissue is white with a pleasant odor and a spicy or bitter taste. All parts of the mushroom stain orange with age or when bruised.
Amycorrhizal fungus,H. repandum is broadly distributed in Europe, where it fruits singly or in close groups inconiferous ordeciduous woodland. This is a choiceedible species, although mature specimens can develop a bitter taste. It has no poisonous lookalikes.
First officiallydescribed byCarl Linnaeus in his 1753Species Plantarum,Hydnum repandum wassanctioned by Swedish mycologistElias Fries in 1821.[8] The species has been shuffled among several genera:Hypothele by French naturalistJean-Jacques Paulet in 1812;Dentinum by British botanistSamuel Frederick Gray in 1821;Tyrodon by Finnish mycologistPetter Karsten in 1881;Sarcodon by French naturalistLucien Quélet in 1886.[6] After a 1977nomenclatural proposal by American mycologistRonald H. Petersen[9] was accepted,Hydnum repandum became the officialtype species of the genusHydnum. Previously, supporting arguments for makingH. repandum the type were made by Dutch taxonomistMarinus Anton Donk (1958)[10] and Petersen (1973),[11] while Czech mycologistZdeněk Pouzar (1958)[12] and Canadian mycologistKenneth Harrison (1971) thought thatH. imbricatum should be the type.[13]
Severalforms andvarieties ofH. repandum have been described. Formsalbidum andrufescens, found in Russia, were published by T.L. Nikolajeva in 1961;[14] the lattertaxon issynonymous withH. rufescens.[15] Formamarum, published from Slovenia by Zlata Stropnik, Bogdan Tratnik and Garbrijel Seljak in 1988,[16] is illegitimate as per article 36.1 of theInternational Code of Nomenclature for algae, fungi, and plants, as it was not given a sufficiently comprehensive description. French botanistJean-Baptiste Barla describedH. repandum var.rufescens in 1859.[17] English naturalistCarleton Rea described the white-fruit bodied version as a variety—H. repandum var.album—in 1922.[18]
Molecular studies have shown that the currentspecies concept forH. repandum needed revision as there was a poor overlap betweenmorphological and molecular species concepts. A 2009phylogenetic analysis of European specimens, based oninternal transcribed spacer and 5.8S DNA sequences, indicated thatH. repandum specimens form two distinctclades, whose only consistent morphological distinction is cap size. These genetic differences foreshadowed the presence of undescribedcryptic species, and that the taxon may currently be undergoing intensivespeciation.[19] A comprehensive genetic study published in 2016 of members of the genus worldwide found that there are at least four species in the broad concept ofH. repandum: two species from southern China, one from Europe and eastern North America, andH. repandum itself from Europe and northern (and alpine southwestern) China and Japan. Although it is missing from Central America, genetic material has been recovered from Venezuela from the treePakaraimaea dipterocarpacea, suggesting it somehow migrated there and had changed hosts.[20]
Thespecific epithetrepandum means "bent back", referring to the wavy cap margin. The varietal epithetalbum means "white as an egg".[21]Hydnum repandum has been given severalvernacular names: "sweet tooth",[22] "yellow tooth fungus",[23] "wood urchin",[24] "spreading hedgehog",[25] "hedgehog mushroom", or "pig's trotter".[7] The varietyalbum is known as "white wood".[21]
The orange-, yellow- or tan-coloredpileus (cap) is up to 17 centimetres (6+1⁄2 in) wide, although specimens measuring 25 cm (10 in) have been documented. It is generally somewhat irregular in shape (possibly being convex or concave at maturity), with a wavy margin that is rolled inward when young.[7] Caps grow in a distorted shape whenfruit bodies are closely clustered.[26] The cap surface is generally dry and smooth, although mature specimens may show cracking.[7] Viewed from above, the caps of mature specimens resemble somewhat those of chanterelles.[27] Theflesh is thick, white, firm, brittle, and bruises yellow to orange-brown. The underside is densely covered with small, slender whitish spines measuring2–7 mm (1⁄16–1⁄4 in) long.[7] These spines sometimes run down at least one side of thestipe.[24] The stipe, typically 3–10 cm (1–4 in) long and1–3 cm (1⁄2–1+1⁄4 in) thick, is either white or the same color as the cap, and is sometimes off-center.[7] It is easy to overlook the mushrooms when they are situated amongstgilled mushrooms andboletes, because the cap and stipe are fairly nondescript and the mushrooms must be turned over to reveal their spines.[28] The pure white variety of this species,H. repandum var.album, is smaller than the main variety, with a cap measuring 2–7 cm (1–3 in) wide and a stipe that is1–3 cm (1⁄2–1+1⁄4 in) long.[21]
Thespore print is palecream. Thebasidiospores are smooth, thin-walled andhyaline (translucent), roughly spherical to broadly egg-shaped, and measure 5.5–7.5 by 4.5–5.5 μm. They usually contain a single, largerefractive oil droplet. Thebasidia (spore-bearing cells) are club-shaped, four-spored, and measure 30–45 by 6–10 μm. Thecap cuticle is a trichodermium (where the outermosthyphae emerge roughly parallel, like hairs, perpendicular to the cap surface) of narrow, club-shaped cells that are 2.5–4 μm wide. Underneath this tissue is the subhymenial layer of interwoven hyphae measuring 10–20 μm in diameter. The spine tissue is made of narrow (2–5 μm diameter), thin-walled hyphae withclamp connections.[24]
BothH. repandum and the varietyalbum contain thediepoxide compoundrepandiol (2R,3R,8R,9R)-4,6-decadiyne-2,3:8,9-diepoxy-1,10-diol), which is under laboratory research to determine its possible effects.[29] Thevolatile organic compounds responsible for the fruity aroma of the mushroom include eight-carbon derivatives, such as1-octen-3-ol, (E)-2-octenol, and (E)-1,3-octadiene.[30]
European studies conducted after the 1986Chernobyl disaster showed that the fruit bodies have a high rate ofaccumulation of the radioactive isotopecaesium.[31]
North American lookalikes include the white hedgehog (Hydnum albidum) and the giant hedgehog (H. albomagnum).H. albidum has a white to pale yellowish grey fruit body that bruises yellow to orange.H. albomagnum is large and paler thanH. repandum.[32]Hydnum umbilicatum is smaller, with caps measuring 3–5 cm (1–2 in) in diameter, and thinner stipes that are0.5–1 cm (1⁄4–1⁄2 in) wide.[33] Its caps are umbilicate (with a navel-like cavity), sometimes with a hole in the center of the cap,[26] unlike the flattened or slightly depressed caps ofH. repandum.[21] Microscopically,H. umbilicatum has spores that are larger and more elliptical than those ofH. repandum, measuring 7.5–9 by 6–7.5 μm.[27] A European lookalike,H. rufescens, is also smaller thanH. repandum, and has a deeperapricot to orange color.[34]Hydnum ellipsosporum, described as a new species from Germany in 2004, differs fromH. repandum by the shape and length of its spores, which areellipsoid and measure 9–11 by 6–7.5 μm. Compared toH. repandum, it has smaller fruit bodies, with cap diameters ranging from 3 to 5 cm (1 to 2 in) wide.[35]
H. repandum is amycorrhizal fungus.[26] The fruit bodies grow singly, scattered, or in groups on the ground or inleaf litter in bothconiferous anddeciduous forests.[7][34][36][37] They can also grow infairy rings.[38] Fruiting occurs from summer to autumn.[22] It is one of the most common of the tooth fungi.[7]
The species is widely distributed in Europe,[39] where, it has been listed as avulnerable species in theRed Data Lists of theNetherlands,Belgium, andGermany;Sweden lists it as being ofLeast Concern.[40] The species is found in thePacific Northwest andRocky Mountains, and with oaks in eastern North America.[7] It does not occur in Canada, but two related species do:H. washingtonianum andH. subolympicum.[41]
| Nutritional value per 100 g (3.5 oz) | |||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Energy | 1,431 kJ (342 kcal) | ||||||||||||||||||||||||||||||||||
56.1 g | |||||||||||||||||||||||||||||||||||
4.3 g | |||||||||||||||||||||||||||||||||||
19.7 g | |||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||
| †Percentages estimated usingUS recommendations for adults,[43] except for potassium, which is estimated based on expert recommendation from theNational Academies.[44] | |||||||||||||||||||||||||||||||||||
DriedH. repandum is 56%carbohydrates, 4%fat, and 20%protein. In a 100 gram reference amount, severaldietary minerals are high in content, especiallycopper andmanganese. Majorfatty acids includepalmitic acid (16%),stearic acid (1%),oleic acid (26%),linoleic acid (48%), andlinolenic acid (20%).Mycosterol is present.[45]
H. repandum is considered to be a goodedible mushroom, having a sweet, nutty taste and a crunchy texture. Some consider it to be the culinary equivalent of thechanterelle.[46] Author Michael Kuo rates it as "great", noting that there are nopoisonous lookalikes and thatH. repandum mushrooms are unlikely to be infested with maggots.
Delicately brushing the cap and stipe of specimens immediately after harvest will help prevent soil from getting lodged between the teeth.H. repandum mushrooms can be cooked bypickling,[47]simmering in milk orstock, andsautéeing, which creates a "tender, meaty texture and a mild flavor."[48] The mushroom tissue absorbs liquids well and assumes the flavors of added ingredients.[48] The firm texture of the cooked mushroom makes it suitable for freezing. Its natural flavor is reportedly similar to the peppery taste ofwatercress,[28] oroysters.[49] Older specimens may have a bitter taste, but boiling can remove the bitterness.[47] Specimens found under conifers can taste "unpleasantly strong".[50] The formamarum, locally common in Slovakia, is reportedly inedible because its fruit body has a bitter taste at all developmental stages.[16]
Hydnum repandum is frequently sold with chanterelles in Italy, and in France, it is one of the officially recognized edible species sold in markets.[38] In Europe, it is usually sold under its French namepied-de-mouton (sheep's foot).[32]H. repandum mushrooms are also used as a food source by thered squirrel (Sciurus vulgaris).[51]
Media related toHydnum repandum at Wikimedia Commons
Data related toHydnum repandum at Wikispecies