Science sheds light on green-glowing shark

A scientific biofluorescent imaging camera and lighting system developed to obtain 4 K imagery is used underwater in Scripps Canyon, San Diego.

What’s weirder than catsharks glowing green in the deep blue sea? Well, researchers using a shark eye to see them.

A research team from the American Museum of Natural History recently announced the wild finding, among the latest of any number of studies of biofluorescence and bioluminescence among fish species — essentially the ability to absorb light spectrum colors or generate them.

More than 180 species of bony fish biofluoresce, or absorb the light colors, including catsharks, which pull in blue and glow neon shades of green in the dark depths.

The biofluorescent green “makes them easier to be seen by the same species,” said museum curator John Sparks, a co-author of the study. It also might help them distinguish sexes — no small advantage in the depths.

The researchers designed a camera that mimicked the shark’s eye and found that the blue range of the color spectrum was all they really saw, said Gorka Sancho, College of Charleston biological oceanographer who has read the report and similar studies.

Biofluorescence is a widespread phenomena in the world, well known to occur in flowers, corals, butterflies, spiders, parrots and marine invertebrates, but only recently described in fishes, he said.

“Fishes see the world very differently than humans,” Sancho said. “It is actually very cool to know that some sharks biofluoresce, to understand how they actually see and how they actually can ‘see’ themselves better thanks to the biofluorescence in their dark ‘blue’ habitats.”

Catsharks are smaller species of the notorious predator, often 2 feet or shorter, named for their catlike eyes, according to the PBS’s Nature website. The names get more bizarre. Species include balloon sharks that pump themselves up with water like blowfish, pajama catsharks and puffadder shysharks.

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