Environmentally relevant concentrations of bifenthrin induce changes in behaviour, biomarkers, histological characteristics, and the transcriptome in Corbicula fluminea.

Bifenthrin (BF) is an insecticide that is commonly used to control agricultural and domestic pests and is widespread in aquatic environments. Although previous studies have found that BF is toxic to aquatic organisms, such a comprehensive study of the mechanism of toxic effects in bivalves is not common. In this study, to assess the toxic effects of BF on bivalves, adult Corbicula fluminea (C. fluminea) were exposed to 0, 1, 5, and 25 μg/L BF for 15 days. Transcriptome analysis revealed that BF exposure significantly altered the expression of genes involved in detoxification, antioxidation, and metabolism. Moreover, the ROS content and GST activity at 25 μg/L treatments were significantly increased (p < 0.05), and significant increases of MDA concentration and CAT activity were observed at 5 and 25 μg/L treatments (p < 0.05). However, AChE activity was markedly inhibited at 25 μg/L treatments (p < 0.05). In addition, vacuolation in the digestive tubules and the hemolytic infiltration of connective tissue were observed at all treatments, and the degeneration of the digestive tubule was observed at 5 and 25 μg/L treatments. In the behavioural assay, the siphoning behaviour of C. fluminea was significantly inhibited at 25 μg/L treatments (p < 0.05), whereas no significant change in burrowing behaviour was observed. Our findings suggested that BF exposure caused changes in detoxification, antioxidation, and metabolism pathways, biomarker activity or concentrations and histopathological characteristics, resulting in changes in behaviour. Therefore, our findings provide a basis for further evaluation of the toxicity of pyrethroid insecticides in bivalves.