Bioaccumulation And Developmental Toxicity Of Typical Pyrethroids On Xenopus Tropicalis Embryos

Amphibians are susceptible to pesticide pollution due to their special living environment and physiological structure.Exposure to pesticides during the early developmental stages of amphibians can adversely affect their entire life cycle.Pyrethroids are widely used chiral pesticides,which can be detected in large quantities in water and have high ecological risks to non-target organisms.However,the research on the developmental toxicity of pyrethroids to amphibians is still insufficient,and the bioaccumulation of pyrethroids in amphibians is still unclear.In this study,bifenthrin(BF)and lambda-cyhalothrin(LCT)were selected as typical representatives of pyrethroids,Xenopus tropicalis as a model organism,and Xenopus tropicalis embryos were exposed to environmentally induced pyrethroids.Toxicity of pyrethroids was determined for early developmental and the differences between enantiomers were analyzed.To further illustrate the absorption and elimination of pyrethroids and their enantiomers by Xenopus tropicalis.According to toxicity of pyrethroids in Xenopus tropicalis,after 7 days exposure,BF and LCT were lethal to tadpoles.Pyrethroids inhibited tadpole growth and development,delayed tadpole development,shortened body length and had teratogenic effects.In this study,behavior and micro-spatial distribution were supplemented as toxicity endpoints.Behavior was sensitivity and accuracy as exercise indicators.This study showed that pyrethroids had strong developmental toxicity to Xenopus tropicalis.And effective toxicity endpoints were screened for the study of early developmental stages of amphibians.The results of enantioselective toxicity of pyrethroids to Xenopus tropicalis tadpoles showed that R-BF was lethal to tadpoles,inhibited tadpole growth and development,and resulted in abnormal tadpole movement behavior,while S-BF had no toxicity to tadpoles.(+)-LCT were stronger than(-)-LCT for the lethality,growth inhibition and behavioral abnormalities,and(-)-LCT had no significant developmental toxicity.Enantioselective toxicity of pyrethroids to Xenopus tropicalis was observed at early developmental stages.The results of bioaccumulation of LCT on Xenopus tropicalis tadpoles by gas chromatography showed that LCT accumulated rapidly in tadpoles,and 2?g/L LCT accumulated continuously in tadpoles with exposure time.The concentration of LCT on tadpoles in the 20?g/L group decreased rapidly after reaching the peak value and decreased to 37.1% at the end of the absorption stage.During the elimination stage,LCT content in tadpoles decreased rapidly.he results of liquid chromatography mass spectrometry showed that LCT isomerization occurred in water,and LCT isomers were also detected in tadpoles.The results of bioaccumulation of LCT enantiomers by Xenopus tropicalis tadpoles showed that there were differences in the absorption,accumulation and elimination of pyrethroids in Xenopus tropicalis tadpoles.At the accumulation stage,the content of(+)-LCT reached peak after 24 hours of exposure,and(-)-LCT reached peak at 6 hours.The peak content of(+)-LCT was more than twice that of(-)-LCT.In elimination stage,the ability of elimination on tadpoles to(+)-LCT was worse than(-)-LCT.Combined with the results of developmental toxicity,the ability of accumulation was stronger and the ability of elimination was worse for LCT enantiomers on tadpoles,the toxicity was stronger.