A lot of reef creatures could be in the red.
A widespread capacity for fish, corals, worms and other animals to fluoresce red has been largely overlooked, contend Nico Michiels of the University of Tübingen in Germany and colleagues in a new study.
Seawater quickly absorbs the red wavelengths of daylight filtering through, so that at depths below 10 meters the red portion of sunlight disappears and the blues and greens dominate. The majority of fish tested so far from this zone have vision tuned to blues and greens.
Reef biologists have treated red as “irrelevant,” Michiels says. Red, however, deserves more attention since a substantial number of reef animals produce their own red glow, he and colleagues say in an upcoming BMC Ecology.
Michiels noticed the red fluorescence in 2007 while diving with a mask that filtered out all but red wavelengths for another project. As he descended, the sun’s available red light dwindled quickly, leaving him in virtual darkness. Then he was startled to see the red fluorescent eyes of a fish, the red fin of another. Since then, he and collaborators have found that 32 reef fishes sampled from 16 genera give off a red fluorescent glow. Substances on their bodies capture light at other wavelengths and release the energy as red light.
Me, I reckon it just looks cool.