False truffle

A false truffle or a hymenogastrale is any species of fungus that has underground fruiting bodies that produce basidiocarps resembling the true truffles of genus Tuber.[1][2] While rodents such as squirrels eat a wide variety of false truffle species, many are considered toxic or otherwise inedible by humans and only a few are sought after as food.[3][4][5][6][7][8]

Melanogaster tuberiformis, a false truffle of the genus Melanogaster.

The rodents exist in an almost symbiotic relationship with the false truffle. The false truffle depends on the rodents to help spread its spores as it does not have the ability to eject the spores themselves. The rodents are attracted to a scent produced by the false truffle and ingest the spores. Spores survive the intestinal tract of the rodents and are excreted in the fecal matter ready to germinate.[9] During the evolutionary period of the false truffle it lost its mushroom cap shape and closed up to protect the spores from dryer or harsher conditions.[8] As a result it lost the ability to discharge its spores and hence the need for animal spore distribution.[9] It is thought that false truffles and truffles evolved to grow beneath the surface because of changing conditions on the surface.[10] Given that fungus is sensitive to moisture and temperatures it makes sense that one strategy of survival would be to go underground where the moisture content is more stable. [10] The stipe also dramatically shortened because it no longer needed the length to help with spore dispersal as a result some species either lost the stipe or it is still found inside the false truffles. Similar in appearance to true truffles which are ascomycetes false truffles are in fact basidiomycetes. Different False truffle lineage can be traced to agarics, russulas, boletes, and chanterelles.[11] All false truffles have a symbiotic mycorrhizal relationship with the trees and shrubs they coexist with. Where the trees give them sugars and they provide the trees with more water and nutrients. Where the interior of the true truffle is marbled and solid.[9] The interior of the false truffle is mostly not marbled like the true truffle instead most will have a pulp like interior.[12] Some species will have a black and white appearance or a brown color other species will have a white interior . [12] The interior will differ according to species. Although there are no known poisonous species of false truffle they are not generally edible to humans. The four most common types of false truffle are Scleroderma polyrhizum, Pisolithus arhizus, Choiromyces meandriformis and Choiromyces magnusii.[13]