Glowing frog a world first

The polka dot tree frog, as it appears under UV light (Nature)
The polka dot tree frog, as it appears under UV light (Nature)

A South American frog has been outed as the world's first fluorescent amphibian.

The polka dot tree frog, which can be found in swamps and forests across most of the continent, is able to absorb light.

Under normal light, the frog bears a muted set of greens, yellows and reds. But at night, it glows in bright green and blues, according to new research published in journal PNAS.

"I think it's exciting," City University of New York marine biologist David Gruber, who has conducted research into animal bioluminescence, told Nature. "It opens up many more questions than are answered."

A pigment in the frogs called biliverdin hinted at the frogs' ability, unique amongst amphibians as far as biologists know. It's been linked to red light in other species, so when the frog glowed green it came as something of a shock.

"We couldn't believe it," said study co-author Julián Faivovich of the University of Buenos Aires.

The frogs' light is about 18 percent as strong as the moon's, enough to see by. It's not clear yet if the polka dot tree frog can even see its own light output, but other species certainly will be able to.

Fluorescence is different from bioluminescence, such as that found in glowworms. The former requires the storage of light, while animals with the latter are able to make their own.

The only other non-aquatic species with fluorescent abilities are a few species of scorpions and parrots.

The researchers expect to find other frogs and amphibians with fluorescent abilities, now that they've confirmed it to be possible.

"I'm really hoping that other colleagues will be very interested in this phenomenon, and they will start carrying a UV flashlight to the field," said Dr Faivovich.