A bright red and green sea turtle filmed in the Solomon Islands is being hailed as the first with the ability to glow known to science.
The hawksbill turtle was thought to be the first reptile scientists had seen with biofluorescence - the reflection of blue light as a different colour, National Geographic reported.
Marine biologist David Gruber, of City University of New York, was in the Solomons in late July to film biofluorescence in small sharks and coral reefs.
During a night dive the fluorescent turtle suddenly came into view, looking like a spaceship, with a patchwork of neon green and red over its head and body, he said.
Gruber followed the turtle for a short while with a video camera but stopped because he did not want to harass the animal. The hawksbill then dived into the blackness of the deep ocean.
No more glowing turtles were seen at sea, but several young hawksbills being kept by locals were found to glow red.
Gruber thought it was too early to say why the hawksbill sea turtles were able to fluoresce.
Eastern Pacific Hawksbill Initiative director Alexander Gaos said the biofluorescence could be a kind of camouflage for the sea turtle in a habitat - such as a coral reef - full of biofluorescing animals.
Gruber said some of the red on the turtle he saw could have come from algae on the shell fluorescing, but the green was definitely from the hawksbill.
While the discovery raised many questions, it could be difficult to study because so few hawksbill sea turtles were left and they were heavily protected.