Last July, scientist David Gruber was in the Solomon Islands conducting research on biofluorescence in sharks and coral reefs, something that has been documented before. Many of us have heard of bioluminescence — in which an animal emits light because of chemical reactions, but biofluorescence is different. Biofluorescent animals reflect the blue light of the ocean as a different color, Time.com reports.
Corals are known to fluoresce, and recent research has revealed the ability in many species of fish, including sharks and rays, and also itty-bitty crustaceans known as copepods, and mantis shrimp (pictured above), National Geographic reports. Researchers were completely shocked to find a marine reptile doing this, however.
“I’ve been [studying turtles] for a long time and I don’t think anyone’s ever seen this,” said Alexander Gaos, director of the Eastern Pacific Hawksbill Initiative. He wasn’t involved in the find. “This is really quite amazing.”
Gruber, a marine biologist with the City University of New York, was busy filming biofluorescence in small sharks and corals, but he and his team had to be wary of crocodiles that frequent the area, he noted. Then suddenly, out of the blue swam the fluorescent hawksbill turtle.
Looming out of the darkness, it looked like a spaceship gliding into view, Gruber said. An alien patchwork of neon green and red covering its head and body.
He captured the colorful creature on a video camera system that used a blue light that matched the blue light of the surrounding ocean. With the aid of a yellow filter on the camera, the scientists were able to pick up fluorescing creatures.
Gruber, a National Geographic “emerging explorer,” spoke with local residents and was introduced to a group of captive turtles of the same species. When he tested them for biofluorescence, all glowed red, Quartz notes. He is in the midst of co-producing a 3D IMAX film about bioluminescence.
This raises many questions, but hawksbill turtles (Eretmochelys imbricata) are critically endangered, and therefore difficult to study, Discovery News reports. Populations of these turtles have declined by 80 percent in the last decade, according to the International Union for Conservation of Nature’s Red List of Endangered Species.
Gruber kept up with the turtle for a brief while, but “after a few moments I let it go because I didn’t want to harass it.” and it descended to the pitch-black depths.
It’s too early to say why these sea turtles have the ability to fluoresce, or if populations in other places also do this, Gaos and Gruber told National Geographic.
“[Biofluorescence is] usually used for finding and attracting prey or defense or some kind of communication,” Gaos said. In this case, the turtle could have been using it as a form of camouflage. The shell of the hawksbill turtle does an excellent job of helping the animal conceal itself in a rocky reef during the daytime, Gaos said.
“When we go out to catch them, sometimes they’re really hard to spot,” he noted.
It could also be difficult to find them in a coral reef loaded with biofluorescing animals.
The red on the hawksbill, for instance, could be due to algae fluorescing on the turtle’s shell, Gruber noted. The green, however, is definitely from the turtle.
Now Gruber has an ocean of questions he wants to explore. Can these turtles see the biofluorescence? Where do they get the ability to do this — do the compounds within their food cause them to fluoresce? Or do they make their own compounds, and, do other sea turtle species do this?
“It’d be fairly difficult to study this turtle because there are so few left and they’re so protected,” Gruber notes.
He thinks he might be able to study the hawksbill’s cousin, the green sea turtle. They are a little bit more common, but also endangered. He added that hawksbill sea turtles are one of the rarest creatures on the planet; sadly for all of their conservation importance, they remain largely mysterious to us.
Note: The video is dazzling and definitely worth watching.
