Scientists could have written an R-rated, gender-bending plot twist to Disney's "Finding Nemo": Clownfish have a natural ability to change their sex.
Clownfish, the aquarium pet of choice since the release of the animated movie, live in such a rigid social structure in the wild that if one of the dominant breeding adults is removed, the size, status and even sex of the other clownfish change rapidly to return the group to the status quo.
"If the female of the group dies, the male changes sex and becomes the breeding female," said Cornell University evolutionary biologist Peter Buston, "while the largest nonbreeder becomes the breeding male."
Some other species of fish are known to do the same thing.
The study of the exotic reef dwellers, named for their outrageous colors, appears in today's issue of the journal Nature.
Buston observed 97 groups of clownfish living on reefs in Papua New Guinea.
Buston did not address how the fish change sex.