On September 29th, 2015 we learned about

Scientists stumble upon surprisingly showy sea turtle

Marine life comes in an amazing range of color, from the bright orange of a clownfish to the blue and yellow stripes of an angelfish. Apparently, it’s not enough though, as over 180 species of coral, jellyfish, rays, eels, etc. have been found to be biofluorescent, reshaping the light that hits their bodies into a range of neon colors worthy of an 80’s music video. The most recent addition to the list is none other than a hawksbill sea turtle (Eretmochelys imbricata), whose electric-yellow shell has somehow slipped under our radar until now.

Shifting the spectrum

In many cases the colors we normally see under white light barely hint at the appearance these animals present to each other, so it’s actually understandable that we’ve missed these glowing animals for so long. The ocean’s water acts like a giant filter, absorbing the blue portion of what we see as white light. Like many animals, some of these fish still want to stand out and be found by their peers, and so their bodies re-emit whatever blue light hits them as bright greens, reds and oranges that will then contrast with the water. When enough of these biofluorescent species are gathered in one location, the concept of camouflage needs to be shifted too. For a fish to avoid looking like an obvious dark shadow among a patch neon coral, it needs to be cloaked in an equally bright color in order to blend in.

For humans to see any of this, we need to take high-powered blue lights to the water to pump up the fluorescing effect. Many creatures in the sea have eyesight adapted to these conditions, but our eyes usually don’t see these shifted colors as over the full range of white light when in the water. By bringing additional blue light, or filtering the blue out entirely with yellow lenses, we’ve been able to see this new range of colors and markings.

From brown to bright

Even as the list of green or red fish has grown, the recently seen fluorescing turtle was still a surprise. The rare, endangered species is the first reptile to exhibit this trait. The turtle’s shell usually appears to be a narrow range of browns and blacks over tan, but the blue-filtering cameras revealed an animal with high contrast patterning of black over bright green, with smatterings of bright red from normally green algae for good measure.

It’s hard to be sure what mechanics were at play in this case, since the turtles are so rare they’re hard to study. The striking look of the shell may be to attract mates, but may actually be intended to help the turtle blend in to it’s vibrant environment near the Solomon Islands. Scientists hope to find related species that similarly fluoresce so that their shells can be more easily studied in detail, so that they can avoid disturbing the already precarious (but also vibrant?) hawksbill population.

Source: Researchers Reveal Covert World of Fish Biofluorescence by AMNH , American Museum of Natural History News & Blogs

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