Tiny frogs found in the depths of the Brazilian rainforest have an unusual characteristic – fluorescent skeletons that may help them communicate with each other.
Scientists think pumpkin toadlets are using their glowing bodies either to signal to fellow toadlets or to warn predators they are poisonous to eat.
They made the surprising discovery while investigating how the frogs interact during mating season, and deciding to shine a UV light on their backs.
They are the latest creatures to have their fluorescence revealed by researchers, with spiders, chameleons and birds sharing similar abilities.
“The fluorescent patterns are only visible to the human eye under a UV lamp,” said Dr Sandra Goutte, a researcher at New York University Abu Dhabi.
“In nature, if they were visible to other animals, they could be used as intra-specific communication signals [with other pumpkin toadlets] or as reinforcement of their aposematic coloration, warning potential predators of their toxicity.
“However, more research on the behaviour of these frogs and their predators is needed to pinpoint the potential function of this unique luminescence.”
The toadlets turned out to have entirely fluorescent skeletons, although this was only visible on parts of their body where bony plates sat underneath very thin skin.
At these sites, the lack of dark pigment cells allowed light to travel easily through the skin, meaning the bone’s fluorescence reflected back and appeared as bluish-white patches.
The scientist compared the fluorescence with other closely related species to demonstrate their bones gave off a comparatively bright light.
As the toadlets are active during the day, the scientists think the UV of sunlight likely creates a glow that is visible to some animals.
In parrots and spiders, similar glowing patches have been shown to play a role in sexual communication.
Last year scientists found that the puffin’s brightly coloured beak also glows under UV light, and suggested this too may play a role in attracting the opposite sex.
The new research was published in the journal Scientific Reports.
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