This chain catshark dwells in the dark night of the deep sea. But without a yellow filter to block out blue light—which some biofluorescent fish have—these neon colors would be invisible.
These luminous animals can reflect the blue light hitting a surface and re-emit it as a different color—the most common being green, red, or orange. Biofluorescence is different from bioluminescence, where animals either produce their own light through a series of chemical reactions, or host other organisms that give off light.
Recent research has found that over 180 species of fish and sharks have unique structures in their skin that enable them to biofluoresce.
People don't really think about the importance of light in the ocean, only a small portion of which is sunlit, John Sparks, curator of fishes at the American Museum of Natural History in New York City, said in a previous interview. In such a dim environment, animals rely on other ways of generating light to communicate with each other.
The fact that so many fish and sharks biofluoresce "tells us organisms are using light in ways we don't even see," Sparks noted.
"It's a hidden world that we're just now beginning to tune into," David Gruber, a marine molecular biologist at City University of New York, said in an earlier interview.
Peek into this hidden world with the following eight pictures of "glowing" animals.
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