Scientists Discover First Fluorescent Frog

Fluorescence in the venter of a male tree frog

"For some things we were planning on doing, we had to illuminate the frog tissues with UV light", said study co-author Julián Faivovich, a researcher at the Bernardino Rivadavia Natural Sciences Museum in Buenos Aires, Argentina, according to New Scientist. The frogs have a tiresome coloring in normal circumstances, but beneath an ultraviolet (UV) light, they glow bright blue and green.

This made them glow a bright fluorescent blue-green.

Fluorescent creatures absorb light from their surroundings in short wavelengths and re-cast that light in longer wavelengths.

The South American polka dot tree frog (Hypsiboas punctatus) nearly looks like a cartoon character from an animated film: friendly hues of greens, yellows and reds, polka dots on its back and the weird superpower of being able to glow in the dark.

Instead of giving off the expected reddish color from the biliverdin, the polka-dot tree frogs glowed a greenish-blue color. These molecules are so far said to be unique among known fluorescent particles in animals - although similar molecular properties can be found in plants. The fluorescence increased the frogs' brightness, or glow, by 19 percent at night with a full moon, and 30 percent during dusk. The team published the find on March 13 in Proceedings of the National Academy of Sciences1. By contrast, it is unclear why the polka dot tree frog has a fluorescent ability, but possible explanations could be for the goal of communication, or to attract a mate. In previous research, scientists have found that some types of fish and turtles can produce a fluorescent light, as well as parrots and scorpions. Three molecules, called hyloin-L1, hyloin-L2 and hyloin-G1, found in the lymph and skin glands were found to cause this glow.

However, in the polka dot tree frog, biliverdin turned out to be a red herring.

The discovery could mean that other amphibious species have a fluorescent glow.

This chemical is known to link to proteins, and it helps certain species of insects to re-emit red light.

Unlike bioluminescence - by which species generate their own light - fluorescence requires some light absorption to work. The frog's glowing appearance was unexpected and it took everyone by surprise.

The researchers now believe there may be many other frogs which are fluorescent. "Maybe we should be looking at every species we catch and trying to see if they fluoresce", David Blackburn at the University of Florida who was not involved in the study, told New Scientist. He encourages other researchers studying tropical frogs to carry a UV flashlight with them.

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