Truffle Genus: Choiromyces

Choiromyces alveolatus ascospore scale = 10 µm Choiromyces meandriformis ascospore scale = 10 µm

Kingdom: Fungi Phylum: Ascomycota Order: Pezizales Family: Tuberaceae Choiromyces venosus ascospore

Spore Characters

Surface: Smooth in youth, but soon developing an ornamentation of pits, spines, or sinuous rods up to 5 µm tall.
Shape and Size: Globose, 10-30 µm in diameter excluding ornamentation.
Wall: Single, 0.5-2 µm thick.
Color in Water: Hyaline to pale brown.
Melzer's Reaction: Not distinctive.
Comments: The ornamentation of spores of Choiromyces species in the Northern Hemisphere is distinctive to the genus. The pitted spores of C. alveolatus (Harkness) Trappe and C. magnusii (Matt.) Paol. resemble micro golf balls. C. meandriformis (Fr.) T. Fr., common in Europe and present but rare in North America, has spores ornamented with sinuous rods that vary greatly in length on a given spore and have a rimmed depression in the tip. Immature spores of that species can be hard to differentiate from spores of some Pachyphloeus species.

View photos of Choiromyces spores

Sporocarp Characters

Shape and Size: Subglobose to irregular, 1-10 cm broad.
Peridium: Pale yellow to yellow-brown, smooth to uneven or lumpy.
Gleba: White to pale yellow or brown marbled with narrow, yellow-brown to brown veins, solid.
Odor: Garlicky, pungent or nauseous.

View photos of Choiromyces sporocarps

Name Derivation

Named by Italian obstretrician and mycologist (1800-1865) Carlo Vittadini (1831) from Greek choer- (pig) and -myces (fungus), hence "pig fungus". Perhaps a reference to the avid manner in which pigs seek this truffle.

Distribution

Europe and North America.
Season: Spring, summer and autumn.
Species known from North Temperate Forests: Three are known, two others are likely to be described after further study. One has been described from Australia and one from South Africa, but molecular data indicate both of these should be transferred to a new genus. One is known from Brazil, C. angustisporus.

Keys and Descriptions

No good keys to the species exist. Hawker (1954) and Ceruti (1960) describe C. venosus (= C. meandriformis) that occurs both in Europe and North America. Choiromyces magnusii is described by Ceruti (1960) and C. alveolatus by Gilkey (1939) (as Piersonia alveolata, Harkness). Montecchi and Sarasini (2000) describe C. meandriformis and C. magnusii.