Sharks glow in dark

STUDY: BRIGHT GREEN HELPS OTHERS OF THEIR SPECIES TO SEE THEM

Helps ocean predators to differentiate sexes.

It may not sound like the best way to go incognito, but some species of shark that lurk on the ocean floor glow a bright green hue visible to others of their kind. Scientists said the had identified the molecules responsible for the marine predators’ biofluorescence, and that it might perform other functions, too, like fighting microbial infection.

The research was published in the journal iScience and pinpoints a previously unknown family of

small-molecule metabolites.

“It’s very different from all the other forms of marine biofluorescence” such as the processes seen in jellyfish and corals, David Gruber, a professor at City University of New York and co-author of the study said.

“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.”

The paper focused on two species, the swell shark and chain catshark, that Gruber studied during scuba dive trips in Scripps Canyon, off San Diego. These are altogether more bashful characters than the great whites or tiger sharks that you might see on TV’s Shark Week. “They’re like one metre long, lay at the bottom, are quite shy and not good swimmers,” said Gruber. What’s more, they dwell at depths of 30 metres or more, where only light at the blue end of the spectrum penetrates – if you started bleeding there, it would look inky black. Gruber and his colleague, Jason Crawford at Yale University, noticed that the sharks’ skin had two tones, light and dark, and after extracting chemicals, discovered a fluorescent molecule only present in the light skin that helps the sharks intake blue light and emit green.

The specific way the sharks’ eyes are configured makes them highly sensitive to light at the blue-green interface, thus creating a sharp contrast between themselves and their nonfluorescent surroundings.

“They have a completely different view of the world because of these biofluorescent properties their skin exhibits and their eyes can detect,” Crawford said.

During his dives, Gruber found the sharks were found in groups, from a pair to up to 10, meaning they are social.

Therefore, one idea for why they have these markings is that they help sharks differentiate sex. – AFP

If you started bleeding there, it would look inky black