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[ Basidiomycota > Russulales > Auriscalpiaceae > Lentinellus . . . ] Lentinellus castoreus by Michael Kuo, 27 August 2025 The species epithet castoreus means "beaver," so this little mushroom joins the menagerie of stem-less, shelving species with saw-toothed gills and mammalian Latin names in the genus Lentinellus. The beaver is usually smaller than the bear (Lentinellus ursinus) or the fox (Lentinellus vulpinus), and it is more likely to feature a growing patch of brown, velvety tomentum that spreads from the point of attachment toward the edges with development. But small bears and foxes are common, and the bear and the fox can also feature a spreading patch, making the beaver hard to identify with confidence. The best way to separate Lentinellus castoreeus from Lentinellus ursinus is by drying your specimens, cleanly slicing their caps, and applying Melzer's reagent or Lugol's solution to the dried flesh. The dried flesh of Lentinellus castoreus turns brown to reddish brown with Melzer's or Lugol's, separating it from ursinus, which has flesh that turns instantly black (a strong amyloid reaction). Lentinellus vulpinus is a harder comparison, since it shares the inamyloid reaction to Melzer's or Lugol's with Lentinellus castoreus. The former species has a more northern, boreal distribution, but the ranges of the two species overlap somewhat; you may need to assess hyphal types (vulpinus lacks skeletal hyphae, while castoreus has them) if you suspect you are examining a somewhat aberrant small, southern, fuzzy-patched Lentinellus vulpinus. Lentinellus angustifolius is a synonym. Thanks to Michelle Lierl for documenting, collecting, and preserving Lentinellus castoreus for study; her collection is deposited in The Herbarium of Michael Kuo. Description: Ecology: Saprobic; growing in groups or in shelf-like clusters on the wood of hardwoods; summer and fall, or over winter in tropical climates; originally described from Switzerland (Secretan 1833) and Sweden (Fries 1838); widespread in Europe, North America, Central America, the Caribbean, South America, and Oceania. The illustrated and described collections are from Illinois and Indiana. Cap: 1.5–4 cm across; fan-shaped to kidney-shaped; planoconvex; pale brown to nearly whitish and bald or fibrillose beneath a dense, brown to rusty brown, velvety patch of tomentum that begins near the point of attachment and grows toward the margin with development. Gills: Radiating from the point of attachment; crowded; with saw-toothed the edges; short-gills frequent; creamy white becoming pale brownish; not bruising. Stem: Absent. Flesh: Thin; tough; whitish to brownish; unchanging when sliced; usually without a blackish line separating the cap surface and the flesh (best assessed with magnification—a magnifying glass or dissecting microscope—of a freshly sliced section from a dried specimen). Odor and Taste: Odor fragrant, or not distinctive; taste strongly peppery. Chemical Reactions: KOH negative on fresh cap surface, or black on the brown tomentum; dried flesh brown (not amyloid) with Melzer's reagent or Lugol's solution. Spore Print: White. Microscopic Features: Spores 3.5–5 x 3–4 µm; ellipsoid; sparsely, finely spiny (difficult to detect with light microscopy); amyloid. Basidia 18–20 x 3–4 µm; subclavate; 4-sterigmate. Pleurocystidia 20–30 x 4–8 µm; clavate to fusiform or lageniform, with or without a mucro; smooth; thin- or thick-walled; hyaline in KOH. Pileipellis a cutis of generative hyphae 2–4 µm wide, smooth, thin- or thick-walled, with upright fascicles of darker, orange-brown hyphae. Skeletal hyphae present in context (especially at the base of the context, just above the hymenium); 3–6 µm wide; thick-walled; slightly gnarled; weakly amyloid (grayish to purplish-orangish in Melzer's). Clamp connections present. REFERENCES: (E. M. Fries, 1838) R. Kühner & R. C. J. E. Maire, 1934. (Miller & Methven, 2000; Petersen & Hughes, 2004; Halling & Mueller, 2005; Kibby, 2017; Woehrel & Light, 2017; Knudsen, 2018; Læssøe & Petersen, 2019.) Herb. Kuo 07280502, 07152505. This site contains no information about the edibility or toxicity of mushrooms. |
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Cite this page as: Kuo, M. (2025, August). Lentinellus castoreus. Retrieved from the MushroomExpert.Com Web site: /lentinellus_castoreus.html |