Some fish species, like bluehead wrasse, can go from female to male thanks to duplicate genes. This process was described in a recent study that was published in the Science Advances journal.
This species lives in groups. Males are large and dominant leaders of their groups and they defend smaller females. When a male dies or gets eaten, the largest female in the group starts to change sex and takes up his role. She only needs a few minutes to take up the leading roles, in a few days her starts changing color, and around 10 days after, her ovaries turn into testes.
The fish can successfully breed as a female and then breed again as a male after the sex change. In a way, they get “the best of both worlds,” according to the co-first author of the study, Erica Todd, who works as a molecular ecologist at the University of Otago in New Zealand.
This is the first study that explains what happens in the fish’s body in order to make the change possible, which has been a mystery for decades.