Shine on you crazy frog. The polka-dot tree frog is the first amphibian known to be naturally fluorescent.
Fluorescence, which happens when a substance absorbs light at one wavelength and emits it at a longer one, is known to occur in some parrots and sea turtles, and a wide variety of fish.
The polka-dot tree frog, which is about 3 centimetres long, is pale green and speckled with white, yellow or reddish spots. It is commonly found all over the Amazon basin and is mainly active at dawn, dusk and night.
Julián Faivovich at the Bernardino Rivadavia Natural Sciences Museum in Buenos Aires, Argentina, made the discovery unexpectedly while studying a pigment in the frog. “For some things we were planning on doing, we had to illuminate the frog tissues with UV light. Then we realised the whole frog was fluorescing,” he says.