The world’s first fluorescent frog has been discovered near Santa Fe in Argentina. Scientists at the Bernardino Rivadavia Natural Sciences Museum in Buenos Aires made the discovery by accident while studying the pigment of polka-dot tree frogs, a species common across the continent.

Under normal light, the frog’s translucent skin is a muted yellowish-brown colour with red dots, but when the scientists shone an ultraviolet light on it, it turned a celestial green. According to one of them, Carlos Taboada, the case is “the first scientific record of a fluorescent frog.” The team studied some 200 more examples to ensure the phenomenon was not due to the frog’s captivity and detected the fluorescent properties in all the specimens.

Maria Lagorio – an independent researcher and expert in fluorescence, who the research team contacted after the discovery – told AFP that the trait is common in aquatic species and seen in some insects, “but has never been scientifically reported in amphibians.”

As a mating device, the fluorescence could help send sound and smell cues, and also help males of the species let females know where they are located. In other words, Lopes believes that this is their way to “coordinate the attraction.” Fluorescent skin pigments absorb light at short wavelengths and re-emit it at longer wavelengths. They are uncommon in animals that live on land but can be found in some underwater creatures such as certain species jellyfish and anglerfish. The glowing frog was found to fluoresce using both lymph and glandular secretions. The chemical that gives the frog its greenish glow had never been found in vertebrates before. The land is already pretty bright and colourful, and the researchers cite a past study that says maybe fluorescence is irrelevant above the water.

However, the retinas similar species of frogs use for night vision seem especially good at viewing the specific colours of light the polka-dot tree frogs fluoresce. That means very little because it’s just a correlation and isn’t even between frogs of the same species. However, there are lots of interesting hints that fluorescence might be a tool these frogs use to recognize each other. Now, the researchers just need to observe lots more frogs and run more experiments.

Finally, this discovery has given scientists a strong hint for the answer to an important question in bio photophysical research: does naturally occurring fluorescence act as a biosignal, or is it simply a non-functional outcome of certain pigments’ chemical structure? In the meantime, we have these cute little glow-in-the-dark frogs to look at.