"The pigments are taking in the blue light that is present at that depth and turning it into yellow to maintain the signal," he said.
He and his colleagues found that the color emitted by the fluorescing skin pigments overlaps exactly with the sensitivity range of one of the receptor sets in the stomatopod's eye.
Since then, Caldwell has found similar yellow-green fluorescence in most of the species in the superfamily, the Lysiosquilloids, that includes L. glabriuscula. Most species in that particular superfamily have a yellow or brown or black mark of some kind that fluorescence in the dim depths can enhance.
"This is most interesting where we have a species living over a fairly broad depth range," he said. "However, in animals that live only in deep water, fluorescence allows them to expand their signaling system to use more color, since they have such good visual systems."
How animals use fluorescence in signaling their own or other species is an area only now being explored, Caldwell said. Marshall last year showed that in some parrots, fluorescence in their feathers plays a role in behavior.
Though most underwater creatures, including crustaceans, octopi, squid and many fish, have limited or no color vision, those that do can take advantage of fluorescence to expand the
Contact: Robert Sanders
University of California - Berkeley