SCIENCE LAB SPECIAL : MOVABLE FEAST

'' A Frog that carries unexplained baggage'' : Last 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 took a different turn.

They found dozens of Rao's intermediate golden-backed frogs in a roadside pond. But they noticed something different about one of the roughly thumb-size frogs that was perched on a twig - a curious growth.

Closer inspection showed that it was a tiny mushroom erupting from the frog's flank.

Mr. Lohit and his friends reported on their find 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 living 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.

Mycelia might grow either on the surface of the amphibian's skin or 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 explain the finding, 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.

But Christoffer Bugge Harder, a mycologist and bonnet mushroom expert at the University of Copenhagen, said Mycena had recently been found to grow on the living roots of trees. [ Jude Coleman ]