Effects of Lifetime Atrazine Exposure on Climbing Ability and Gut Integrity in Aged Drosophila melanogaster

ABSTRACT Atrazine is a commonly used herbicide that is often detected outside of agricultural systems. Early‐life exposure is known to negatively affect a variety of traits in both vertebrates and invertebrates. However, the cumulative effects of lifetime exposure on health span (the period of life spent in good health) remain poorly understood. We used Drosophila melanogaster to investigate the effect of lifetime atrazine exposure on two critical health span indicators: mobility and gut epithelial integrity. Flies were reared and aged for up to 27 days on media containing atrazine dissolved in distilled water at concentrations ranging from 0 to 20 ppm. Mobility was assessed via negative geotaxis climbing assays, whereas gut integrity was measured using the “smurfing” dye‐leakage assay. Atrazine exposure significantly increased smurfing rates. This effect was sex specific and observed in females but not males. Furthermore, the relationship between atrazine concentration and gut leakage followed a nonmonotonic dose–response curve, with the highest smurfing rates occurring at the intermediate concentration of 2 ppm. Atrazine exposure did not significantly affect climbing ability in either sex. Both smurfing rate and climbing height were affected by age. Increased smurfing rates due to atrazine exposure were observed in as young as 6‐day‐old females. There was, however, no significant interaction between age and atrazine treatment for smurfing, suggesting that atrazine's effects do not intensify with advancing age. Together, these findings suggest that chronic atrazine exposure negatively affects health span by deteriorating gut integrity in a sex‐specific and nonlinear manner.