Atrazine feminizes sex ratio in Blanchard's cricket frogs (Acris blanchardi) at concentrations as low as 0.1 μg/L.

We exposed Blanchard's cricket frogs (Acris blanchardi) to ecologically relevant concentrations (0, 0.1, 1, and 10 μg/L) of a commercial formulation of atrazine throughout the larval period to determine effects on survival, somatic growth and development (time to metamorphosis and mass at metamorphosis), and gonadal development (sex ratio at metamorphosis and the prevalence of testicular ova in phenotypic males). We tested the following hypotheses: 1) atrazine feminizes the sex ratio, 2) atrazine increases the proportion of phenotypic males with testicular ova, and 3) atrazine differentially affects somatic growth (mass at metamorphosis) and development (time to metamorphosis) for males and females. Although the control sex ratio was male-biased, exposure to 0.1 and 10 μg/L atrazine feminized sex ratios, because these treatments produced 51 and 55% fewer males than the control, respectively. We did not observe testicular ova. Atrazine did not impact survival or metamorphosis, and we did not detect sexually dimorphic impacts on time to metamorphosis or mass at metamorphosis. However, males metamorphosed 2.3 d later than females, regardless of treatment. Sex biases in timing of metamorphosis are underexplored in anurans, but if prevalent, could have important implications for theory surrounding the impact of environmental factors on metamorphosis. Our data suggest that cricket frog sex ratios are sensitive to environmentally relevant concentrations of atrazine and that feminization in the field is likely. Environ Toxicol Chem 2018;37:427-435. © 2017 SETAC.