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'Glowing' biofluorescent sea turtle looks like a reptilian UFO

An endangered sea turtle surprises scientists by showing off an otherworldly glow underwater.

That back of the sea turtle shines green and red. Video screenshot by Amanda Kooser/CNET

It looked like a UFO floating underwater, glowing softly beneath the surface near the Solomon Islands in the South Pacific. The colors were green and red, like flecks of neon. Marine biologist David Gruber was amazed. It was a biofluorescent hawksbill sea turtle, the first known to be recorded, he says.

National Geographic unveiled an exclusive video Monday showing the turtle, which was found while researchers were filming biofluorescent coral. Gruber described it as looking like "a bright red and green spaceship."

Biofluorescence happens when a living creature absorbs blue light and re-emits it as a different color. It's a separate phenomenon from bioluminescence, a chemical reaction that creates light, like with fireflies.

Other marine life, like certain fish and marine eels, are known to be fluorescent, but reptiles haven't been included in that category. That makes the rare turtle a distinct mystery. "Until we actually get ahold of one of these turtles and really start to look at it chemically, we wouldn't know what it is," Gruber said in the video.

Gruber double-checked the findings with some captive hawksbill sea turtles and was able to replicate the biofluorescence.

The discovery raises a series of questions. Does the biofluorescence serve a purpose for the turtles? It could have implications for communication or mating, or may be a form of camouflage.

The hawksbill sea turtle is listed as critically endangered, making it challenging to study due to its rarity. Scientists may be able to follow up the findings by studying other, more common sea turtles. Until more research is done, the "glowing" turtles will remain a fascinating puzzle.