A tiny mushroom collected in Florida contains both psilocybin, the compound that makes "magic" mushrooms hallucinogenic, and amatoxins that can destroy the liver, a combination researchers say they have not seen before, Live Science reported. The findings, on a species called Galerina indica and nicknamed the "dark magic mushroom," were published in Current Biology. The largest specimens were only about 0.2 inches (0.5 centimeters) tall, with caps up to about 0.1 inches (0.25 centimeters) wide, and grew on moss-covered palm trunks in Florida swamps.
The research team, including study co-author Matthew E. Smith, a plant pathologist at the University of Florida, was not looking for a particular toxin when it began collecting Galerina mushrooms. Galerina includes more than 300 species worldwide, many of them poisonous. Chemical analyses showed that the Florida specimens contained both psilocybin and amatoxins, including one amatoxin that had never been documented in mushrooms. Finding amatoxins was not wholly unexpected, because other Galerina species produce closely related compounds, co-author Kunik said. Finding them together with psilocybin was. "To find them both together in one mushroom, I never expected to find that," Smith told Live Science. "We were shocked."
By comparing G. indica's genes with those of other psilocybin-producing mushrooms, the researchers found that the genes shared a common evolutionary origin even though the mushrooms themselves are distantly related. G. indica's psilocybin-producing genes are arranged in a different order than in other such fungi, a clue that the gene cluster was rearranged after jumping between species. The team estimates that G. indica acquired the ability to produce psilocybin through horizontal gene transfer from unrelated fungi about 15.5 million years ago, Smith said, though it is possible the genes entered the lineage twice, perhaps as recently as 6 million years ago. Horizontal gene transfer, more familiar in bacteria, can also move toxin or drug-related genes among fungi. Past work has shown that deadly Amanita mushrooms share amatoxin genes with the unrelated genera Galerina and Lepiota in the same way.
Hannah Reynolds, a fungal ecologist at Western Connecticut State University who was not involved in the study, called the combination and the rearranged gene cluster "very cool." Kunik speculated that producing two incapacitating chemicals could be a powerful defense against being eaten, because an animal would have difficulty evolving resistance to both, but that idea remains a hypothesis. The paper does not suggest that people should pick or eat the mushroom. The verified result is a chemical and genetic description of a very small Florida fungus that carries both a hallucinogen and a liver toxin, a pairing researchers had not previously documented.