By Susan Milius
Seen in the right light, yellow reef fish become spotty pains in the tail fin.
Members of one damselfish species use facial patterns of speckles and swooshes to identify the fish species they regularly attack, researchers report in an upcoming issue of Current Biology. These markings show up only in ultraviolet light, says visual ecologist Ulrike Siebeck of the University of Queensland in Brisbane, Australia.
In tests, Siebeck and her colleagues found that male Ambon damselfish could tell their own species from another just by seeing the ultraviolet markings. When UV light was blocked by filters, confused males picked fights with the wrong rivals.