The genotoxicity of atrazine in the cnidarian Hydra magnipapillata

Abstract

Previous mutagenicity studies of atrazine, an agricultural herbicide, indicate that it can be genotoxic, although results are highly variable and dependent on the type of study organism, the concentration, and the assay used. Here I measured the genotoxic effects of atrazine on the freshwater cnidarian, Hydra magnipapillata. Hydra were exposed to eight concentrations of atrazine representing a range of ecologically relevant and extreme doses (0, 0.003, 0.01, 0.1, 2.5, 10, 20, and 30 ppm) for 96 hours and then the comet assay was used to assess DNA damage. Median tail moment and 90th percentile tail length (indicators of DNA damage) were assessed. I found that DNA damage has a non-linear relationship to atrazine concentration. The highest levels of DNA damage occurred at the mid-range test concentrations (0.1 and 2.5 ppm), which produced tail moments significantly greater (5-7 times) than at 0 ppm. Tail moments of Hydra treated with 10 and 20 ppm atrazine were also significantly greater (2-4 times) than the control. However, 0.01 and 0.003 ppm concentrations yielded no significant difference from controls. Tail lengths followed a similar pattern, but only the 0.1 and 2.5 ppm treatments were significantly different from the control. These results suggest that two or more mechanisms of DNA damage may be involved in the genotoxicity of atrazine. Additionally, preliminary methylation-sensitive restriction fingerprinting (MSRF) analysis was conducted on DNA from Hydra treated with 0. 0.003. and 0.01 ppm atrazine to determine if atrazine exposure could alter DNA methylation patterns. No areas of differential banding were identified. Due to shortcomings of the assay, it remains unclear whether methylation patterns may change in response to atrazine exposure.