Effects Of Three Neonicotinoid Pesticides On The Behavior,Histopatholgy And Antioxidant System Of Asian Freshwater Clams (Corbicula Fluminea)

Neonicotinoids,broad-spectrum systemic insecticides,have been the fastest growing class of insecticides in modern crop protection.China is the largest producing and exporting country of neonicotinoid insecticide.However,with the gradual increase in usage,its potential harm to aquatic organisms has become increasingly prominent.In this study,determination of siphonate rate,tissue sectioning,enzyme activity detection and RT-PCR were deployed.Therefore,in current study,to investigate the effect of neonicotinoid pesticides on benthic bivalves,adult Asian clams(Corbicula fluminea)were exposed to 0,20,200,and 2 000 ?g/L imidacloprid,thiamethoxam and clothianidin for 30 days respectively.Neonicotinoid pesticides significantly inhibited the siphoning and burrowing behavior(P < 0.05)of the clams.Significant histopathological changes were associated with degeneration of the cilium,contraction and adhesion of the lymphocyte,and swelling of epithelium cells in gills,and there was notable degeneration of the digestive tubules,hemolytic infiltration of the connective tissue and epithelium cell necrosis in the digestive glands at the 2000-?g/L treatments.The activity of ACh E in the digestive glands was significantly inhibited at all treatment levels(P < 0.05).Additionally,indicators of the antioxidant system(e.g.,SOD,CAT,and GST activity)and MDA content were significantly increased in the gills and digestive glands for all treatments(P< 0.05).Moreover,the m RNA expression levels of hsp genes(hsp 22,40,60,70)and multixenobiotic resistance(MXR)system-related genes(abcb1,abcc1)were significantly downregulated(P < 0.05).Therefore,our results suggest that all the three neonicotinoid pesticides changes the oxidative stress,cellular detoxification,and MXR system of C.fluminea which made the abnormal behavior,injured pathological structure and imbalance of antioxidant system.These also indicated that the residual pesticide contentaccumulated in water and sediment did have certain potential harm to benthic organisms,which in turn will affect other non-target aquatic organisms and even human body.In this regard,the effects and mechanisms of neonicotinoids on benthic bivalves need to be given enough attention and in-depth research.