How does this polka dot tree frog glow in the dark?
At first glance, the South American polka dot tree frog gives off a pale, brownish-green hue. But under a fluorescent light, it glows bright green, with 18 percent of a full moon鈥檚 light.
in Proceedings of the National Academy of Sciences, a team of Argentinian and Brazilian researchers attribute this phenomenon, known as fluorescence, to compounds secreted by the frog鈥檚 skin and lymph glands. They see their finding as a major step forward for our understanding of amphibians.
鈥淲e were not expecting this bio-fluorescence,鈥� study co-author Norberto Peporine Lopes . 鈥淚t was an incredible surprise.鈥�
Unlike bioluminescent animals, like fireflies and anglerfish, which generate their own light, fluorescent animals absorb light and re-emit it at a longer wavelength. Scientists had seen this phenomenon at work in sharks, sea turtles, and other species, but never in amphibians.
When the researchers set out to investigate the polka dot tree frog鈥檚 pigment, they thought they might find red fluorescence. The frogs contain a chemical called biliverdin, which has been known to bond to proteins and help some insects fluoresce red.
But the frog, known as Hypsiboas punctatus to scientists, instead glowed green under the researchers鈥� blacklight. 鈥淲e couldn鈥檛 believe it,鈥� another team member, herpetologist Juli谩n Faivovich, told Nature.
Further investigation found that three molecules 鈥� hyloin-L1, hyloin-L2 and hyloin-G1 鈥� were responsible for the phenomenon. Dr. Lopes, a chemist at Brazil鈥檚 University of S茫o Paulo, these molecules are unique among known fluorescent animals.
What purpose could these molecules serve? Scientists are now gearing up to answer that question. Bibiana Rojas, an ecologist at the University of Jyv盲skyl盲 in Finland, 聽鈥渋t would be interesting to investigate if [fluorescence] has a role in species recognition, or whether it facilitates the formation of couples.鈥�
鈥淔luorescence would be potentially very useful in a noisy environment and in a habitat with dense foliage, as it would make individuals brighter,鈥� she continued.
While the threats facing frogs , scientists keep identifying new strategies they may have for adapting and thriving in a wide range of environments. Last month, 海角大神 reported the discovery of several new species of 鈥渕iniature鈥� frogs, whose tiny bodies may have evolved in response to a limited food supply.
It鈥檚 too early to know definitively why South America鈥檚 frogs evolved fluorescence, and whether South America鈥檚 250 other translucent-skinned tree frogs also have the trait. But Dr. Faivovich is eager to find out.
鈥淚'm really hoping that other colleagues will be very interested in this phenomenon,鈥� , 鈥渁nd they will start carrying a UV flashlight to the field.鈥�
