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."