Atrazine Feminizes Male Frogs

The popular herbicide atrazine can chemically castrate male frogs and transform them into functional females capable of producing viable eggs, a new study shows (Proc. Natl. Acad. Sci. USA, DOI: 10.1073/pnas.0909519107). Previous work demonstrated the weed killer’s gender-bending effects on larval amphibian development, but this study, spearheaded by Tyrone B. Hayes of the University of California, Berkeley, is the first to explore atrazine’s developmental effects on reproductive function and fitness at sexual maturity. Hayes’s group exposed an all-male group of African clawed frogs to environmentally relevant concentrations of atrazine from their tadpole phase to up to three years after they’d become frogs. Although 100% of the larvae were genetically determined to be male, 10% of the frogs developed into females that mated with unexposed males and produced viable eggs. “The impacts of atrazine on amphibians and on wildlife in general are potentially devastating,” write the researchers. “The negative impacts on wild amphibians is especially concerning given that the dose examined here is in the range that animals experience year-round in areas where atrazine is used.”