The potential mutagenic and genotoxic effects of the herbicide atrazine were investigated in different developmental stages of Dendropsophus minutus tadpoles. These animals were exposed to 4 nominal concentrations of atrazine (2.25, 4.5, 9, and 18 mg/L) and 40 mg/L of Cyclophosphamide as a positive control, for 96 h. Negative controls were also added to the experiment. The tadpoles were divided into three groups according to Gosner's developmental stages, namely GS 25-33 as premetamorphic, GS 36-39 as prometamorphic, and GS 42-43 as metamorphic climax. Our results showed that the premetamorphic and metamorphic stages were more sensitive than the prometamorphic stage to the herbicide. A comet assay and micronucleus test for the sensitive stages demonstrated DNA damage in a concentration-dependent curve. Although a dose-response effect was not observed for the prometamorphic stage, a statistically significant difference was found between the treatment of 18 mg/L and the negative control. Moreover, the highest concentration of atrazine showed both the largest amount of DNA damage and the highest micronucleus frequency regardless of the developmental stage of D. minutus. In conclusion, atrazine was genotoxic and mutagenic for D. minutus in a dose-sensitive manner, dependent on larval developmental stages. Considering the prometamorphic stages showed no dose-response effect to atrazine, we suggest caution when using this stage in biomonitoring studies in order to avoid false negative results. Amphibians have been proven to be useful bioindicators, and we suggest replicating biomonitoring studies using different species to represent ecosystems' environmental impacts.
Keywords: Genotoxicity; Herbicide; Mutagenicity; Susceptibility; Tadpole.
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