Exploring the effect of atrazine exposure on the reproductive capacity of Daphnia magna

Atrazine is an herbicide commonly used for weed control in crops and on turf, but environmental contamination with atrazine causes endocrine disruption leading to reproductive defects in humans and freshwater organisms. The molecular and cellular mechanisms causing these reproductive deficiencies remain largely unknown. Thus, the purpose of this study is to explore the reproductive consequence of atrazine exposure at the molecular and cellular level in the freshwater planktonic crustacean, Daphnia magna. Results show that exposure of D. magna to high atrazine concentration of 1000 or 2000 μg/L reduced the number of the first set of offspring born at least 5 days after atrazine exposure. D. magna exposed to these atrazine concentrations exhibited DNA fragmentation, nuclear condensation and fragmentation in the ovaries, and caspase-3 protein activation in both the ovaries and embryos in the brood chamber. No obvious DNA fragmentation, nuclear condensation and fragmentation, or caspase-3 activation was seen in other tissues. These findings suggest that high environmental concentrations of atrazine specifically induce apoptosis in reproductive tissues, which could account for the decline in the number of offspring in D. magna exposed to high concentrations of atrazine.