Some sharks that live close to the ocean bed are able to generate a bright green glow that other sharks from the same species can detect. Scientists said on August 8th. The molecules that enable them to do that, known as biofluorescence, have been discovered, AFP has reported.
These molecules could play a role in combatting microbial infection. "It's very different from all the other forms of marine biofluorescence.
This is a small molecule rather than a protein and it shows that in the blue ocean animals are independently evolving this ability to absorb blue light and transform it into other colours,” David Gruber, a professor at City University of New York and co-author of the study published by iScience, told AFP.
The swell shark and the chain catshark were the subjects of the study that was conducted via scuba diving trips in Scripps Canyon, off the coast of San Diego.
These sharks are very shy compared to the great white and tiger sharks. "They're like a metre long, they lay at the bottom, they're quite shy and they're not good swimmers," said Gruber. Where they live, 30 metres or more below the surface, only blue lights are visible.
Chemicals extracted from the sharks’ skins showed a fluorescent molecule only found in the light parts of the skin. This molecule enables the sharks to absorb blue light and release green. Their eyes evolved to be very perceptive of light in the blue-green spectrum, which makes them very distinguishable from the non-fluorescent environment.
"They have a completely different view of the world that they're in because of these biofluorescent properties that their skin exhibits and that their eyes can detect," Crawford, Gruber’s colleague, said in a statement.
Within their own group these sharks are social and can be observed in groups of up to ten members, so their signature glow could help in identifying mating partners or could be an individual marker.
"We really don't have a firm grasp on shark biology and they're just incredibly amazing creatures with all kinds of fascinating superpowers, from their incredible sense of smell to their ampullae of Lorenzini that allows them to feel electricity and detect the heartbeats of prey hiding in the sand. These are sharks that have been right off the pier at San Diego, and yet we're just now discovering this mystery."