Glowing Red Fish Discovered
September 22, 2008--The reef fish Enneapterygius pusillus has found a creative way to communicate with other fish in a world dominated by blues and greens: The fish literally glows red.
At least 32 species of reef fish that live at depths below 33 feet (10 meters) possess this unique method of signaling, researchers said in a September 2008 study.
Because the color red has a longer wavelength and fish are better attuned to seeing colors with shorter wavelengths (such as green and blue), scientists had thought red was irrelevant to fish.
"Marine fish are generally assumed not to see or use red light, with the exception of some deep-sea fish," lead researcher Nico Michiels of the University of Tuebingen in Germany said in an email.
"Our discovery shows that there is a lot of red fluorescence that is very indicative of an active role of red in fish communication."
(See photo: "Blind Sea Creature Hunts With Light" [July 8, 2005)
The study appeared recently in the journal BMC Ecology.
--Kimberly Johnson
—Photographs by Michiels et al./BMC Ecology 2008
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.
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.
—Photographs by Michiels et al./BMC Ecology 2008
It's not just fish that appear red--several species of invertebrates and algae, including this calcareous alga in the genus Amphiroa, also send out a scarlet glow.
More research is needed into the role color plays in how fish see the world, scientists say.
"This is a phenomenon that deserves further investigation, but its functional significance remains unclear," Gary Grossman of the University of Georgia, said of the September 2008 study.
"It is possible this fluorescence serves as a signaling function in fish, but one wonders what its significance could be in … invertebrates that lack eyes."
It's not just fish that appear red--several species of invertebrates and algae, including this calcareous alga in the genus Amphiroa, also send out a scarlet glow.
More research is needed into the role color plays in how fish see the world, scientists say.
"This is a phenomenon that deserves further investigation, but its functional significance remains unclear," Gary Grossman of the University of Georgia, said of the September 2008 study.
"It is possible this fluorescence serves as a signaling function in fish, but one wonders what its significance could be in … invertebrates that lack eyes."
—Photographs by Michiels et al./BMC Ecology 2008
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