Toxicity Evaluation Of Spirotetrama To Zebrafish(Danio Rerio)

Spirotetramat(developed by Bayer Crop Science company)is a unique and highly potent insecticide having both phloem and xylem mobility,widely used to control sucking pests and spider mites.Currently,this insecticide is one of the first batch of recommended pesticide products,and has been applied better and popularized more widely on vegetables and tropical fruit in Hainan Province,and its technical patent had expired in March 16,2016.However,spirotetramat can transfer more into aquatic environments,which may cause more damage to aquatic organisms,and the details of the environmental risk and aquatic toxicity of spirotetramat have not been fully investigated.Therefore,it has been found necessary to assess systematically the toxicity of spirotetramat on aquatic organisms as a reference for the Hainan ecological safety.In this study,zebrafish(Danio rerio)was chosen as research subject to assess the toxicity of spirotetramat.The study investigated:the acute toxicity of spirotetramat on zebrafish embryos development;the acute toxicity of spirotetramat on zebrafish larvae and the chronic toxicity of spirotetramat on zebrafish larvae.The results were as follows.1.Our results demonstrated that spirotetramat was moderately toxic to zebrafish embryos.After exposed 96 hpf,acute LCso and 95%confidence limits for spirotetramat were estimated to be 4.06(3.92-4.21)mg/L.Spirotetramat was negative effects in embryonic development with a concentration dependent manner after 10 hour exposure.Moreover,spirotetramat exhibited reduction in hatching rate and body length,increasion in yolk sac oedema and pericardial edema.and caused bent spine,tail deformities and other poisoning symptoms.In addition,exposure to spirotetramat resulted in increases in voluntary movement of the tail swing,and reduction in heart rate and melanin.2.The study indicated that exposed to spirotetramat resulted in significant increases in apoptosis not only in zebrafish brain tissue,but also in heart,spinal and tail region by using AO staining and TUNEL staining at 96 hpf.Using real-time quantitative PCR,this present study reported that up-regulation of the mRNA expression of p53,Bax and Caspase-3.The high expression level of p53,significantly,was 3.27-fold greater than the control.Therefore,we speculated that apoptosis induced by spirotetramat on zebrafish embryo was mainly through the high expression level of p53 into mitochondrion pathway.3.The acute toxicity of spirotetramat on zebrafish larvae was moderately toxic.After exposed 96 hpf,acute LC50 and 95%confidence limits for spirotetramat were estimated to be 3.64(3.34-3.99)mg/L.The abormal behaviors of zebrafish larvae after exposured to spirotetramat included swimming retardation and imbalance of body.Moreover,the results indicated that zebrafish larvae has been induced to DNA damage when exposure to spirotetramat by using micronucleus assay and DNA laddering assay.4.Apoptosis and oxidative stress were induced in liver of zebrafish larvae after exposing spirotetramat for 28d.Using AnnexinV-FITC/PI staining assay,the results indicated that spirotetramat resulted in significant increases in apoptosis on liver tissue,showing dose-dependent patterns of toxicological effects.Moreover,apoptosis in male liver was more than the female.Using qRT-PCR,this present study reported that the gene expression of antioxidant system enzyme Mn.-SOD,Cu/Zn-SOD,CAT,gpx 4a and gpx 4b were changed in zebrafish liver when exposed to spirotetramat,related to oxidative stress.