The common labrid fish, Pseudocheilinus evanidus, emits a red luminescence that can be seen at close distances.

Seawater absorbs sunlight's red wavelengths, making normally red objects look black or gray below 33 feet (10 meters), researchers said in September 2008.

The fish do not produce light but instead use pigments to convert incoming blue-green light wavelengths into red, lead researcher Nico Michiels of the University of Tuebingen in Germany said in an email.

"In some cases, the red fluorescence may actually be part of camouflage, as the reef itself fluoresces in very irregular, but partly strong patches," Michiels added.