You’re on a night dive in the Solomon Islands to film biofluorescence in small sharks and corals. Your underwater camera system includes a blue light and a yellow filter that blocks out blue light, allowing you to see biofluorescent organisms. Suddenly, a “bright red-and-green spaceship” glides by. It’s a sea turtle. And it’s fluorescing, too.
This is what happened to marine biologist David Gruber, who recorded the critically endangered hawksbill sea turtle “glowing” on video. It’s the first time that a reptile has been shown to fluoresce — to absorb light and re-emit it at a lower energy level as a different color — and further investigation of other local hawksbills have shown the same ability.
What use might biofluorescence be to a sea turtle? Perhaps it helps with finding mates, or camouflaging, or perhaps it works to their advantage in a way that we haven’t imagined yet, but we do know that any creature with a yellow intraocular filter sees the glowing patterns on the sea turtle’s shell and head.
Watch this next: The Difference Between Bioluminescence and Fluorescence. Plus: More turtle videos.