Chameleons are known amongst scientists for their unique and impressive abilities.
From their independently rotating eyes to their rapid tongues, these colour-changing reptiles have more than one trick up their sleeve.
Researchers from LMU Munich have now discovered that many species also have bony tubercles on their heads that glow under UV light.
“It has long been known that bones fluoresce under UV light, but that animals use this phenomenon to fluoresce themselves has surprised us and was previously unknown,” says Dr Frank Glaw, curator of herpetology at the Bavarian State Collection of Zoology.
Biogenic fluorescence is well known in marine organisms, but uncommon in terrestrial vertebrates.
“We could hardly believe our eyes when we illuminated the chameleons in our collection with a UV lamp, and almost all species showed blue, previously invisible patterns on the head, some even over the whole body,” says David Prötzel, lead author of the new study.
The tubercles are covered with transparent skin, allowing UV light to emit clearly from the bone below. They form distinct, unique patterns, and are much more numerous in males than in females, suggesting some role in sexual selection.
Although further studies are needed for confirmation, scientists conclude these patterns are not coincidental, but are used in conspecific recognition, and allow individuals to transmit a consistent pattern from beneath their ever-changing skin.
Main image: One of the chameleons under UV light. © David Prötzel