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Colpoma quercinum

[ Ascomycota > Rhytismatales > Rhytismataceae > Colpoma ... ]

by Michael Kuo

This fascinating little fungus is "erumpent," which the Dictionary of the Fungi (Kirk et al., 2008) defines as "bursting through the surface of the substratum." If you have seen the 1979 film Alien, you may recall actor John Hurt playing the substrate for an erumpent extraterrestrial. Colpoma quercinum does more or less the same thing to oak twigs, shoving itself through the bark, then opening its spore-bearing surface.

The mature fungus is only a few millimeters across, and consists of a smooth, yellowish surface that is surrounded by a thin layer of brownish black tissue. Under the microscope, it features fantastic needle-shaped spores that are packed into the asci side by side, along with amazing paraphyses that project past the asci and begin to curve, coil, and spiral.

The species illustrated and described here, from Illinois, may or may not be the same as the "true," European Colopoma quercinum--but its color, spore sizes, and oak habitat make quercinum the best match. Colpoma juniperi is grayish, has shorter spores, and appears on sticks of junipers--while Colpoma crispum is bluish gray, has shorter spores, and appears on the sticks of spruces. A poorly-known species, Colpoma californicum, features a yellow surface, longer spores, and appears on twigs of canyon oak, in California.

A recent molecular study (Lantz and collaborators, 2011) found the genus Colpoma, as it is currently conceived, to be somewhat incoherent; they suggest the genus "needs to be redefined," and suspect that Colpoma juniperi may not be closely related to Colpoma quercinum.

Description:

Ecology: Parasitic and saprobic; growing gregariously on the living and fallen twigs of oaks; spring and early summer; North American distribution uncertain but probably widespread east of the Rocky Mountains. The illustrated and described collections are from Illinois.

Fruiting Body: Disc-like; 2-5 mm across; roughly circular in outline when viewed from above; upper surface yellow, bald, smooth; encasement surrounding the edges and underside of the disc, brownish black, tissue-like, with a torn outer edge; odorless.

Microscopic Features: Spores 70-90 x 1-2 µ; needle-shaped; smooth; often curved; hyaline in KOH. Asci 140-175 x 10-15 µ; subclavate to subfusiform, with subacute apices; hyaline. Paraphyses 150-250 x 1 µ; filiform; projecting well beyond asci; apices developing curls and spirals; hyaline.

REFERENCES: (Persoon, 1796) Wallroth, 1833. (Fries, 1822; Saccardo, 1883; Ellis & Everhart, 1892; Twyman, 1946; Cash, 1958; Darker, 1967; Dennis, 1968; Breitenbach & Kränzlin, 1984; Minter, 1988; Lantz et al., 2010.) Herb. Kuo 05040704, 04211202.

 

Colpoma quercinum

Colpoma quercinum

Colpoma quercinum

Colpoma quercinum
Spores

Colpoma quercinum
Asci and paraphyses

Colpoma quercinum
Paraphyses



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Kuo, M. (2015, April). Colpoma quercinum. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/colpoma_quercinum.html