Gymnopus dryophilus
Description
This honey-brown to buff-brown, hygrophanous Gymnopus lives up to its species name, seldom venturing far from oaks. A close cousin, Rhodocollybia butyracea, is similarly colored but has a lubricous cap, gills with finely scalloped edges, a cream spore print with a hint of pink, and a faintly striate stipe. It is more common under conifers but can occur in other habitats.
Gymnopus dryophilus is a mushroom commonly found in temperate woodlands of Europe and North America. It belongs to section Levipedes of the genus, is characterized by a smooth stem having no hairs at the base.
A large number of Gymnopus and Rhodocollybia species look for all the world like Gymnopus dryophilus on casual observation. For help sorting these mushrooms out, see the key to collybioid mushrooms - or, if you are comfortable separating Rhodocollybia butyracea from Gymnopus dryophilus but you would like to fine tune your species concepts within the "Gymnopus dryophilus group," see the table and comments below.
A jelly fungus parasite, Syzygospora mycetophila, sometimes attacks Gymnopus dryophilus, causing pale, tumorous growths on the stem, gills, and cap; see the linked page for illustrations.
Edible, but opinions vary on its culinary value; the stipes are tough and should be discarded.
Common names: Oak-loving Collybia (Gymnopus), Small Tan.
Mushroom Identification
Ecology
Saprobic; growing alone, scattered, gregariously, or loosely clustered; growing from litter or twigs, in almost any hardwood, conifer, or mixed forest ecosystem; spring, summer, and fall (and in winter in warmer climates); widely distributed in North America.
Cap
1-7.5 cm; convex with an incurved margin when young, becoming broadly convex to flat; moist; bald; dark reddish-brown to brown when young, becoming tan to orangish brown to very pale buff.
Gills
Attached to the stem or free from it; whitish to pinkish, becoming buff; crowded.
Stem
1-10 cm long; 2-7 mm thick; equal (occasionally slightly flared to base); dry; pliant and fibrous; bald; whitish above, light buff below, becoming darker; soon hollow; usually with thin, whitish rhizomorphs attached to the base.
Flesh
Whitish; thin.
Chemical Reactions
KOH negative to faintly yellowish-olive on cap surface.
Spore Print
White to creamy or pale yellowish-white.
Microscopic Features
Spores: 5-6.5 x 2.5-3.5 µ; smooth; elliptical; inamyloid. Pleurocystidia absent. Cheilocystidia 15-50 x 2-6 µ; clavate, subclavate, cylindric, or irregular; often branched, lobed, or with coralloid projections. Pileipellis of branched and swollen, interwoven hyphae 2-13 µ wide.
Medicinal Properties
Antiinflammatory activity
One study extracted a β-glucan (MW=1.237 x 106 Da) consisting of (1→3) and (1→4) glucosidic linkages and named Collybia dryophila polysaccharide (CDP). CDP was shown to strongly inhibit nitric oxide production in activated macrophages, suggesting that this polysaccharide displays a potential anti-inflammatory activity (Pacheco-Sanchez et al., 2006).
The effect of CDP was evaluated on nitric oxide (NO) production induced by lipopolysaccharide (LPS) and gamma interferon (IFNγ) or by LPS alone in RAW 264.7 cells. CDP significantly inhibited NO production in a dose-dependent manner without affecting cell viability. The inhibition of NO by CDP was consistent with decreases in both inducible nitric oxide synthase (iNOS) protein and mRNA expression suggesting that CDP exerts its effect by inhibiting iNOS gene expression. Also, CDP at concentrations of 400 and 800 µg/ml was shown to significantly increase prostaglandin E2 (PGE2) production in LPS- and IFNγ-induced macrophages when compared to the control (Pacheco-Sanchez et al., 2007).
History
The Russet Toughshank was described in 1790 by French mycologist Jean Baptiste Francois Pierre Bulliard, who gave it the scientific name Agaricus dryophilus. 31 years Later Paul Kummer renamed it Collybia dryophila, by which name it was widely known until very recently. The currently-accepted scientific name dates from 1916, when American William Alphonso Murrill proposed the transfer of this species to the genus Gymnopus, whereupon its name became Gymnopus dryophilus.
Synonyms of Gymnopus dryophilus include Agaricus dryophilus Bull., Omphalia dryophila (Bull.) Gray, Collybia dryophila(Bull.) P. Kumm., Collybia dryophila var. aurata Quél., Marasmius dryophilus (Bull.) P. Karst., Collybia dryophila var. alvearis Cooke, Marasmius dryophilus var. auratus (Quél.) Rea, and Collybia dryophila var. oedipoides Singer.
Gymnopus, the generic name, comes from Gymn- meaning naked or bare, and -pus meaning foot (or, in the case of a mushroom, stem). The specific epithet dryophilus comes from Greek and means 'lover of oak leaves', which seems appropriate because this mushroom is found most often growing in the leaf litter beneath oak trees.
Photo sources:
Photo 1 - Author: pinonbistro (CC BY-SA 4.0)
Photo 2 - Author: User:Strobilomyces (CC BY-SA 2.5)
Photo 3 - Author: pinonbistro (CC BY-SA 4.0)
Photo 4 - Author: AJ (j7u) (CC BY-SA 3.0)
