What You Should Know
Catathelasma imperiale is a conifer-loving species defined by its large size, its gills (which begin to run down the stem), its white spore print, its stem (long and rooting, with a tapered base), its sticky brownish cap, its mealy odor, and its double ring.
In Europe, this species has something of an iconic status amongst mycologists as an impressive and remarkable mushroom to find.
It occurs in western North America and in various European countries (mainly in central Europe) where its frequency varies from "fairly rare" to "rare". It is included in the Red Lists of 15 European countries and is considered declining everywhere due to eutrophication, habitat destruction, and habitat change.
Catathelasma imperial is edible but tough-fleshed. It is said to be good pickled.
Other names: Commander, Imperial Cap, Wurzel-Möhrling (Austria), Hiidloorik (Estonia), Náramkovec Císařský (Czech Republic), Keisersopp (Norway), Náramkovka Cisárska (Slovakia).
Catathelasma imperiale Mushroom Identification
Presumably mycorrhizal; growing alone or scattered on the ground under conifers; late summer and fall; common in monsoon season in the Rocky Mountains, where it often grows under Engelmann spruce and subalpine fir; western North America.
10-40 cm; convex becoming planoconvex or nearly flat; sticky when young (but soon dry); with pressed-down fibers or scales; dark brown to brown, reddish-brown, or yellowish-brown; the surface often cracking up in maturity.
Running down the stem or beginning to do so; close; whitish or vaguely yellowish, sometimes discoloring grayish with age.
Up to 18 cm long and 8 cm wide; tapering to the base and usually rooting somewhat; sometimes almost completely underground; whitish above the ring; brownish below; with a flaring, double ring in which the upper edge of the upper ring is often lined, and the lower ring is often flimsy or nearly gelatinous.
White; hard; not changing on exposure.
Odor and Taste
Taste strongly mealy; odor strongly mealy.
Spores 10-15 x 4-6 µ; smooth; elongated-elliptical; amyloid. Basidia up to 75 µ long.
Catathelasma imperial Bioactive Compounds
Eight ergostane-type sterols and three of their derivatives (one mono-linoleate and two mono-glucosides), were isolated from the ethyl acetate soluble fraction of Catathelasma imperiale (Yang et al., 2003). Two of the sterols were previously unknown: 22E, 24R-ergosta-7, 22-diene-3β, 5α-diol-6β-linoleate and 22E, 24R-ergosta-7, 22-diene-3β, 5β, 6α-triol. These compounds have an uncommon cis-fused A/B ring.
Catathelasma imperiale Medicinal Properties
Antitumor effects. Polysaccharides extracted from the mycelial culture of C. imperiale and administered intraperitoneally into white mice at a dosage of 300 mg/kg inhibited the growth of both Sarcoma 180 and Ehrlich solid cancers by 90% (Ohtsuka et al., 1973).
Catathelasma imperiale Taxonomy and Etymology
Catathelasma imperial is the only species of Catathelasma known in Europe. It was first described in 1845 by Fries under the name Agaricus imperialis. In 1872 Quélet classified the species in Armillaria and in 1922 the Austrian botanist Günther Beck von Mannagetta und Lerchenau invented the separate genus Biannularia for this single species, making it Biannularia imperialis. The genus Catathelasma had been defined in 1910 by Ruth Ellen Harrison Lovejoy based on the American species C. evanescens and for a time the two genera were regarded as separate (though closely related), as in a 1936 paper by Rolf Singer. A few years later in 1940, Singer united the genus using Lovejoy's name, which takes precedence.
The epithet "imperiale", meaning "imperial" refers to the (at times) large size of the mushroom. The species name must end in "-e", not "-is", as the genus is neuter.
Photo 1 - Author: Ge Z-W, Wu J-Y, Hao Y-J, Zhang Q, An Y-F, Ryberg M (2020) The genus Catathelasma (Catathelasmataceae, Basidiomycota) in China. MycoKeys 62: 123-138. https://doi.org/10.3897/mycokeys.62.36633 (Public Domain)
Photo 2 - Author: Szabi237 (Creative Commons Attribution 3.0 Unported)
Photo 3 - Author: Sava Krstic (sava) (Creative Commons Attribution-Share Alike 3.0 Unported)