While filming the Solomon Islands’ biofluorescent reefs in late July, marine biologist David Gruber and his team discovered something quite unexpected: into the frame swam a large hawksbill turtle, its shell illuminated with vivid shades of neon green and red. The turtle stayed with the team for several minutes, allowing them to capture never-before-seen footage of the world’s first known biofluorescent reptile.
A phenomenon discovered relatively recently, biofluorescence refers to an organism’s ability to reflect blue light hitting a surface, and re-emit it as a different color. It is most often seen in corals, but has also been detected in a host of other marine creatures, including fish, sharks, rays and mantis shrimp. Biofluorescence is not the same as bioluminescence, a similar phenomenon wherein organisms generate their own light through a series of chemical reactions.
The most common biofluorescent colors are green, orange and red. Previously, it was thought that an organism could only emit a single color, but the footage of the Solomon Islands turtle glowing both green and red challenges this assumption. Gruber, of City University of New York, hypothesized that the red biofluorescence may be separately generated by algae clinging to the turtle’s shell, but when he examined captive juvenile hawksbills kept by one of the islands’ local communities, he found that their shells also glowed red.
The discovery has raised a number of exciting questions, including how the turtles generate their biofluorescence, and whether the ability is limited to the Solomon Islands population. Gruber is eager to study other turtle species, including the green sea turtle, to see whether they also possess biofluorescent abilities. In the wake of Gruber’s recent discovery, scientists are particularly keen to find out the purpose behind the turtles’ glow-in-the-dark tendencies.
Director of the Eastern Pacific Hawksbill Initiative Alexander Gaos told National Geographic in a recent interview that “biofluorescence is usually used for finding and attracting prey, or defense, or some kind of communication.” Gruber comments that the hawksbill’s mottled shell provides the turtle with incredible camouflage as it moves amongst the reef’s rocky outcrops during the day. He theorizes that perhaps the biofluorescence serves the same purpose at night, helping the turtle to blend into a reef alive with glowing corals.
The recent discovery also shines a spotlight on the plight of the hawksbill turtle, a critically endangered species pushed to the brink of extinction in recent decades by the demand for tortoiseshell. With global populations struggling to recover from a 90 percent decline, Gruber says that it will be “difficult to study this turtle because there are so few left.” Hopefully, however, the new interest in the species sparked by his recent discovery will help to generate support for hawksbill conservation projects around the world.
