World’s first glow-in-the-dark frog discovered

Washington: Scientists have discovered the world’s first fluorescent frog in Argentina that sports a muted palette of greens, yellows and reds under normal light, but gives off a bright blue and green glow in the dark. The ability to absorb light at short wavelengths and re-emit it at longer wavelengths is called fluorescence, and is rare in terrestrial animals. Until now, it was unheard of in amphibians. Researchers found that the South American polka dot tree frog uses fluorescent molecules totally unlike those found in other animals. Many ocean creatures exhibit fluorescence, including corals, fish, sharks and one species of sea turtle. On land, fluorescence was previously known in only parrots and some scorpions. It is unclear why animals have this ability, although explanations include communication, camouflage and mate attraction, researchers said. They expected to find red fluorescence in these frogs, because they contain a pigment called biliverdin. Normally, biliverdin turns the amphibian’s tissues and bones green. However, in some insects, proteins bound to biliverdin emit a faint red fluorescence, said Carlos Taboada, from the University of Buenos Aires in Argentina. However, in the polka dot tree frog, biliverdin turned out to be a red herring. When researchers trained a ultraviolet A flashlight (or black light) on polka dot tree frogs collected near Santa Fe, Argentina, they were astonished to find the animals gave off an intense greenish-blue glow instead of a faint red. Three molecules in the animals’ lymph tissue, skin and glandular secretions were responsible for the green fluorescence. —