Enantioselective Effect Of Chiral Insecticide Fipronil On Development And Locomotor Behavior In Embryonic-Larval Zebrafish

Fipronil, one of the potent and effective phenylpyrazole insecticides,is widely used for agricultural and domestic pest control. Although fipronilis characterized as low mammalian toxic, it has been proved highly toxicto bees and aquatic organisms. Furthermore, as a chiral compound, fipronilusually interact with biological systems selectively and may result indifferent aquatic toxicity. In recent years, growing concern is paid toinvestigate the adverse effect and enantioselective toxicity of fipronil onaquatic invertebrates. However, information on enantioselectivedetrimental effect of fipronil on aquatic vertebrates such as fish is notavailable. Therefore, the primary objective of this study was to evaluatethe enantioselective effects of fipronil on locomotor behavior anddevelopmental toxicity in embryonic-larval zebrafish. Details of our study were listed as follows:（1） Zebrafish （AB strain） were used to study the effect of fipronil on earlydevelopmental toxicity and locomotor activity. Results indicated thatfipronil induced malformations including uninflated swim bladder, bentspine and reduced body length as well as mortality of zebrafish.Locomotor activity assay showed the average speed of larvae wassignificantly higher than control at low concentration （40μg/L） and lowerat high concentration （160μg/L）. Besides, photoperiod stimulation testrevealed larvae exposed to fipronil at high concentration were moresensitive than that at low concentration.（2） The enantioselective effect of fipronil on locomotor behavior anddevelopmental toxicity in embryonic-larval zebrafish was investigated.Results indicated the developmental toxicity of fipronil on zebrafish wasenantioselective and the toxicity order was racemate＞S-（+）-＞R-（-）-enantiomer. Furthermore, the photoperiod stimulation results demonstratedthat there were no differential effect between two enantiomers andracemate at low concentration while larvae were significantly moresensitive to racemic fipronil than two enantiomers at high concentration.（3） The joint effect on the developmental toxicity of fipronil and Cu²⁺on zebrafish was studied by two-factor analysis of variance methods.Significant interaction on inhibiting the hatching of zebrafish embryo wasobserved when exposed to the mixture of fipronil and Cu²⁺, while no significant interaction existed on the mortality and curved body axis.The present study demonstrated that fipronil was adverse on the earlydevelopment and locomotor behavior of zebrafish, and enantioselectivitywas observed between two enantiomers on the early development ofzebrafish. Our study is useful for broadening our knowledge to realize theenvironmental risk of fipronil.