A Mushroom Grew in a Strange Place: The Side of a Frog
Maybe frog and fungi are friends.

A group of Indian herpetology hobbyists did not expect to find a mushroom growing out of this Rao’s intermediate golden-backed frog, but there it was. Lohit Y.T./WWF photo

By Jude Coleman
February 12, 2024

Over the summer, Lohit Y.T., a river and wetlands specialist at World Wildlife Fund-India, set off with his friends in the drizzly foothills of the Western Ghats in India. They had one goal: to see amphibians and reptiles.

“There were five of us, busy searching for the species and avoiding leeches,” Mr. Lohit said.

But their herpetology hunt turned into a fungus find.

Dozens of Rao’s intermediate golden-backed frogs were in a roadside pond. But the crew noticed something different about one of the frogs perched on a twig — a curious growth. Upon closer inspection, they realized it was a tiny mushroom erupting from the roughly thumb-size frog’s flank, like an itty-bitty fungal limb. In other words, a mushroom sprouting from a living frog.

Mr. Lohit and his friends published a note on their discovery in January in the journal Reptiles and Amphibians.

After Mr. Lohit posted pictures of the frog online, citizen scientists and mycologists chimed in to say that the fungal hitchhiker resembled a type of bonnet mushroom. Bonnet mushrooms, collectively called Mycena, typically live on decaying plant matter, like rotting wood. So, how did one end up sprouting from a frog?

Very few fungi make mushrooms. For a mushroom to grow, a fungal spore has to set up shop on a surface and produce mycelia. Mycelia are threadlike cells that absorb nutrients, not unlike a plant’s root. If the mycelia find enough nutrients, the fungus can produce a mushroom.

That adds to the puzzle of the fungi and the frog. Mycelia are either on the surface of the amphibian’s skin or further inside its body, said Matthew Smith, a fungal biologist at the University of Florida who was not involved with the finding. But the team didn’t collect the frog or the mushroom, having planned only to observe. So, it’s impossible to say exactly what was going on, he said.

Scientists have found fungi growing where they normally shouldn’t in the past, but Dr. Smith had never heard of a mushroom on living animal tissue. “I was very surprised to see it,” he said.

While no one can say for certain what kind of mushroom it was, it bore a resemblance to a bonnet mushroom.Credit...Lohit Y.T./WWF-India

Fungi thrive in a spectrum of ecosystems. In addition to decomposing scrap vegetation in woodlands, some live peacefully on or in living organisms. Our own skin is home to fungi such as yeast.

But sometimes fungi living on critters are pathogens. Take Ophiocordyceps, for example, the insect-infecting, parasitic fungus behind “zombie ants.” Or the fungus Batrachochytrium dendrobatidis, chytrid for short, which causes a deadly disease in frogs.

Mr. Lohit’s frog shroom doesn’t seem to be a pathogenic fungus, experts said. But even though the frog was alive and seemingly well at the time of the discovery, there’s no way of knowing without investigating further whether the fungus was negatively affecting the animal or whether it was in danger of croaking.

The mushroom’s identity will also remain a mystery because mycologists need more than a photo for identification. Sydney Glassman, a fungal ecologist at the University of California, Riverside, isn’t convinced that the growth is even a mushroom. Further evidence — obtaining a genetic sample or seeing the gills and spore color — is needed to make an identification, she said.

Christoffer Bugge Harder, a mycologist and bonnet mushroom expert at the University of Copenhagen who was not involved with the work, says it looks like a Mycena — although it may be a look-alike. “If I were to bet my money on a fungus that could have this lifestyle,” he said, it would be Mycena.

Dr. Harder and his colleagues recently discovered that Mycena grows not only on decaying wood but also on the living roots of trees. That means the genus, which contains hundreds of species, can pull an ecological 180, switching from decomposer to parasite or mutualist.

Mushrooms are abundant on the forest floor during monsoon season, when Mr. Lohit and his friends found the frog, said Sonali Garg, a herpetologist at the Museum of Comparative Zoology at Harvard who was not involved with the finding. She has studied frogs in the Western Ghats and other parts of India and had never seen anything like this before, either. But she noted that the region’s warm, humid environment was ideal for mushrooms. Combine that with a frog’s dewy skin and it could be the perfect storm for mushroom growth, she said.

Although experts agree that more information is needed to draw conclusions, they said that the finding will get people thinking about nature and fungi.

“Reports like these are important,” Dr. Garg said. “Maybe it will make people go out and look more closely.”