He Said, She Said

Pesticide reverses sex of some male frogs

Gender symbols A pesticide that is used around the world can turn male frogs into egg-producing females, a new study has shown.

The pesticide, atrazine, has infiltrated water supplies and can travel to areas hundreds of kilometers from the place where it was originally used. Some research has suggested that atrazine can affect the development of amphibians, but these findings have been disputed.

A team exposed male African clawed frogs (Xenopus laevis) to atrazine and monitored their growth. Ten percent of the frogs developed female anatomical traits, and two of these newly-female animals were able to mate with males and lay eggs. Atrazine-treated male frogs also had lower levels of testosterone, mature sperm, mating success, and fertility than males that had not been exposed, the researchers found.

These reproductive failures could threaten the survival of wild amphibian populations, the authors warn in the Proceedings of the National Academy of Sciences. Frogs that become female through sex reversal are still genetically male and will always produce male larvae. This trend could further increase the chances of extinction, the team says. – Roberta Kwok

Source: Hayes, T.B. et al. 2010. Atrazine induces complete feminization and chemical castration in male African clawed frogs (Xenopus laevis). Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0909519107.

Image © powershot, iStockPhoto.com