Scientists get peek into how some fish change sex as adults

If in the beginning there was male and female, fish seem to have forgotten the memo. For nearly 500 fish species, including the clownfish in "Finding Nemo," the great divide between sexes is more like a murky line: If circumstances call for it, the fish can swap their sex, with females turning into males in some species and males turning into females in others. The researchers looked at the bluehead wrasse, a reef fish that swims in small groups of a dominant blue-headed male and a posse of smaller yellow females.