Fishes' sex-change secret revealed - New Scientist

Fishes' sex-change secret revealed
11 February 2006
From New Scientist Print Edition.

FISH are the gender-benders par excellence of the animal kingdom, and a study of cells from the testes of trout is helping to reveal why.

Goro Yoshizaki and his team from Tokyo University of Marine Science and Technology in Japan investigated the germ cells from adult male rainbow trout that normally give rise to sperm. When they took these cells and transplanted them into the body cavities of female hatchlings, they migrated to the host fishes' ovaries. There they developed into eggs that when fertilised grew into healthy offspring (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0509218103).

This cellular flexibility may explain why fish are susceptible to feminisation by pollutants that mimic the female hormone oestrogen. It also probably underpins the ability of some species to change sex as they mature, to maximise their reproductive success. Some even change back and forth repeatedly.

Yoshizaki hopes his finding can be put to practical use by fish breeders. Bluefish tuna, in particular, are highly prized for sushi in Japan, but populations are declining worldwide. This new technique may help boost egg stocks.