Imagine swimming through the ocean at night with a pair of underwater lights. You are searching for corals to capture images for National Geographic. It’s almost pitch black, and most of the ocean’s wildlife is not visible without your light source. Out of nowhere, a large mass glowing bright red and green swims right beneath you. It’s not a lamp. It’s not the sun. It’s a biofluorescent sea turtle!
This event was a reality for marine biologists filming in the coral reefs of the Solomon Islands. David Gruber of City University of NY and his team were exploring the ocean for National Geographic on July 31. As they were filming, a friendly hawksbill sea turtle (Eretmochelys imbricate) swam below them, most likely intrigued by the lights the photographers were using.
“This turtle seemed completely attracted to the blue lights that we were filming with and just swam right into me,” said Gruber. “It was absolutely gorgeous.” The turtle emitted neon green and red fluoresence throughout its head, shell, and legs. Gruber described the turtle to be like an “alien spaceship” swimming through the galaxy of the ocean.
This curious turtle was the first biofluorescent marine reptile in the wild, a crucial discovery in the field of biofluorescence.
Turtles, however, were not the first animals to be seen as biofluorescent. John Sparks, another marine biologist, and his team identified more than 180 different species of bioflouresent sharks and fish. They noticed that many of these species were camouflaged well under white light, but under flourescent blue light, they were strikingly bright.
Biofluorescence is the phenomenon when high energy light waves are absorbed and transformed into lower energy waves. These light waves are then emitted, forming a “glowing” effect. Biofluorescence allows scientists to understand more about cellular biology. Different molecules can be modified to emit fluorescence without being destructed. These color differences allow scientists to locate certain cellular proteins easily.
The ocean is the perfect place for wildlife to evolve for biofluorescence, for the animals living in the ocean are constantly surrounded by blue light. The ocean is blue because every light is absorbed except for blue. Blue light, one of the stronger colored lights is then transformed into a lower intensity colored light such as red, green, orange, or yellow by these animals.
But why would animals in the ocean need to glow? What is the point of biofluorescence? Although the discovery of biofluorescence in animals is a fairly new occurrence, some scientists have made a few hypotheses to why these animals glow. One guess is that the animals use fluorescence to identify each other within a species. It’s possible that certain lights that one species emits cannot be seen by another species, allowing for a visual cue between species, without being noticed by predators. Another suggestion is that biofluorescence could be used as a lure for prey, similar to an angler fish. Glowing also could be a false signal that an animal is poisonous because in the wild, many animals that have bright and vibrant pigments are seen as a threat.
The sad part about this discovery is that hawksbill turtles are critically endangered, and there is still so much that humans haven’t learned about them. Gruber explains how “we still don’t understand them” and there is a greater “sense of urgency to protect and understand this species while they are still here.”