Endangered Hawksbill Sea Turtle Is Biofluorescent — Why Is A Complete Mystery

Shelley Hazen - Author

Sep. 29 2015, Updated 5:00 a.m. ET

While marine biologist David Gruber was out for a night dive near the Solomon Islands, something that looked a lot like a spaceship emerged from the black depths of the ocean. The truth of what he saw that night was even morning amazing — a biofluorescent turtle.

The turtle Gruber captured on film glowing neon green and red is a rare Hawksbill sea turtle, a nearly-extinct marine reptile that remains a complete mystery to scientists, Newsweek reported.

And the turtle is now the only known marine reptile to be biofluorescent. Plenty of other creatures have this ability, including sharks, rays, tiny crustaceans called copepods, and mantis shrimp. But this discovery is a first.

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“I’ve been [studying turtles] for a long time and I don’t think anyone’s ever seen this,” Eastern Pacific Hawksbill Initiative Director Alexander Gaos told National Geographic. “This is really quite amazing.”

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To be biofluorescent simply means that the turtle is able to reflect the blue light hitting its surface and then bounce it back with a different color, usually green, red, or orange. This is different from bioluminescence, in which an animal produces its own light via chemical reactions or host bacteria.

Gruber headed to the Solomon Islands in late July not to study Hawksbill sea turtles, but to film biofluorescent small sharks and coral reefs. One night with his colleagues, he was diving in the ocean on watch for crocodiles, when the glowing turtle emerged, reminding him instantly of an alien craft.

He flicked on his camera, outfitted with a blue artificial light that matches the light in the ocean and a yellow filter that allowed him to capture biofluorescent creatures, the International Business Times added. The video he captured of the biofluorescent turtle made its way online, along with the historic announcement of its unexpected discovery.

Gruber said he followed the Hawksbill for a while, then “let it go because I didn’t want to harass it.” The last he saw of it, the turtle dove downward and disappeared in the black depths of the ocean.

And now, science has a mystery to solve. Why do these turtles biofluoresce? How? Are they the only marine reptiles who can?

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Trouble is, the Hawksbill’s endangered status means that Gruber and other biologists won’t be able to easily study them because they’re very well protected. Their population is sparse as well, with their total worldwide population dwindled to 90 percent of what it once was.

The turtle is closely related to the green sea turtle, however, which is much more common — though also endangered — and scientists may be able to study this creature in its place.

Luckily that night after Gruber emerged from the ocean, he was able to study the Hawksbill a bit more. A nearby community kept several young turtles in captivity, and he was able to determine that they were biofluorescent as well. They glowed neon red.

So far, science has some theories about why the turtle is biofluorescent. It could be a defense mechanism, a way to find or attract prey, a form of communication, or a method of camouflage. In the daytime, when they’re not emitting brilliant neon colors, the turtle’s shell does an excellent job of concealing it among the rocks on shore.

Then there are the questions about whether the turtle can see its biofluorescence, where the ability originates (the options: absorbing fluorescent compounds from food or making their own), how they use it, whether the Hawksbill is just one of many sea turtles that are biofluorescent, and if the creatures glow the same in other environments.

[Photos Courtesy Rich Carey, Mike Veitch / Shutterstock]


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