Effects of α-cypermethrin enantiomers on the growth, biochemical parameters and bioaccumulation in Rana nigromaculata tadpoles of the anuran amphibians

•(S)-(1R, 3R)-α-cypermethrin was 29 times more toxic than (R)-(1S, 3S) to tadpole.•α-cypermethrin can enantioselectively inhibited the tadpole growth.•α-cypermethrin can enantioselectively enhance the antioxidant enzyme activities.•Accumulation and elimination of α-cypermethrin in tadpole were enantioselective.

Populations of many amphibian species are declining worldwide in part because of pesticide contamination. As a surface water contaminant, α-cypermethrin may have severe ecological impacts on amphibians. Here, we examined the acute toxicity of α-cypermethrin enantiomers to dark-spotted frog Rana nigromaculata tadpoles at 24, 48, 72 and 96 h, finding that the tadpoles were indeed sensitive to α-cypermethrin. The (S)-(1R, 3R)-enantiomer was approximately 29 times more toxic than the (R)-(1S, 3S)-enantiomer at 96 h. A significant delayed growth in R. nigromaculata tadpoles after exposure to 0.5 µg L−1 of S-(1R, 3R)-cypermethrin was observed. Additionally, increased superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST) and malondialdehyde (MDA) levels indicate the presence of oxidative stress in the tadpoles. Further, tadpoles exposed to sublethal concentrations of α-cypermethrin enantiomers exhibited enantioselective growth and oxidative damage. Bioaccumulation experiments showed that the tadpoles could rapidly accumulate α-cypermethrin. The (R)-(1S, 3S)-enantiomer was preferentially accumulated over the (S)-(1R, 3R)-enantiomer, and it was also eliminated more quickly, as evidenced in the subsequent depuration experiments.

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