A fluorescing frog.
A fluorescing frog. Taboada et al/PNAS

In Argentina, the polka-dot tree frog is common. But even though it is a species familiar to humans, the frog was hiding a special power.

It is fluorescent, as a team of scientists reports in the Proceedings of the National Academy of Sciences. When UV light shines on a polka-dot tree frog, it reemits that light at a lower frequency, glowing a vivid green.

The frog without fluorescence.
The frog without fluorescence. Taboada et al/PNAS
The frog with fluorescence.
The frog with fluorescence. Taboada et al/PNAS

It’s rare to find fluorescent animals on land; the only other land vertebrates known to fluoresce are parrots. The scientists examining the frogs expected that they might give off a low and dull red light but were surprised when it turned bright green.

The frog under UV lighting and under normal lighting.
The frog under UV lighting and under normal lighting. Taboada et al/PNAS

It turned out that the frog’s skin has a fluorescent compound not found in other fluorescent vertebrates (which include, besides parrots, marine turtles). This discovery opens up the possibility that there are many more fluorescent land animals, and one of the study co-authors, Julián Faivovich, told Nature that he now intends to examine 250 tree frogs to see if they also have a secret glow.