Fish that glow red

Red Zones
Seen above is a striking photo of a triplefin reef fluorescing red. According to new research, many reef animals glow red but that capacity is usually overlooked scientists because most of that wavelength of sunlight is absorbed out as you go more than 10 meters down into the ocean. As a result, most animals from that zone see blue and green best. But University of Tübingen evolution ecologist Nico Michiels and his colleagues suggest that the red-glowing fish carry an untold biological story about the spectrum of the sea. From Science News:

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…

Most of the red-fluorescing fish are small and likely to have mates or neighbors close by, so red glows would make good short-range signals for courtship or other local business, Michiels suggests. The idea that seawater has rendered red ineffective "is a kind of dogma we are attacking," he says. "I would hope that the whole light ecology of reefs is reconsidered."

"Fish glowing red" (ScienceNews)