Toxic Fungi of Western North America

by Thomas J. Duffy, MD

Gyromitrin group

The toxic species of Gyromitra are brown, yellow brown or reddish brown. Like other species of Gyromitra they do not have gills under the cap, but bear their spores on the wrinkled saddle-shaped cap or on one with a ±brain-like convoluted surface. Grey or black species of Helvella, which are similar, but simpler in configuration, contain little or none of the pretoxin, gyromitrin (the protein framework plus the active hydrazine toxin it holds).

Western Gyromitra species that contain gyromitrin are Gyromitra esculenta (Fr.) Fr. and Gyromitra infula (Schaeff. Ex Fr.) Quél. Gyromitra gigas and fastigiata contain Gyromitrin in Europe, but probably not here. (135) There is no evidence that Gyromitra gigas (Krombh.) Quél. sensu McKnight and Gyromitra korfii (=Gyromitra fastigiata sensu McKnight) have caused any poisonings in North America. (125)

The taxonomy of Gyromitra gigas and closely allied species is somewhat unsettled because of European confusion about the type collections. (136) Although Gyromitra esculenta, fastigiata and the gigas/montana group are eaten regularly, poisonings are quite rare in Western North America. There are traces of gyromitrin in Helvella crispa, lacunosa and elastica and possibly in Gyromitra sphaerospora. The distribution of Gyromitra sphaerospora appears to be restricted to Montana and adjacent areas of the Northern Rocky Mountains.

Gyromitra esculenta has the usual dry to moist, hollow, brain-shaped convolutions on a 3-10 cm irregular subglobose head on a hollow stipe. The color of the convolutions externally varies from clay brown to a darker bay brown; internally the convolutions and the stipe are a pallid off-white. The stipe is 2-5 cm long and 1-2.5 cm thick, white to pale brown, but often tinted with a dark pinkish to reddish brown color reminiscent of the cap. The stipe is fairly smooth, round to somewhat compressed or grooved, hollow, although the remaining central canal may be small.

Helvella and the other non-gilled genera containing gyromitrin (usually in lesser amounts) have other non-standard mushroom shapes—saddle, disk, spatula etc. and are not described here, except to note that Helvella is similar, but with a more simple shape, commonly resembling a saddle. These other non-gilled genera include such species as Otidea onotica, Cyathipodia macropus, Spathularia flavida, Leotia lubrica and Cudonia circinans. (137)