Mechanisms of developmental toxicity in zebrafish embryos (Danio rerio) induced by boscalid

Boscalid has been widely used for controlling various plant diseases. It is one of the most frequently detected pesticides in main coastal estuaries in California, with concentrations as high as 36μg/L, but its ecotoxicology information is scarce. To assess the aquatic risk of boscalid, acute toxicity and sub-lethal developmental toxicity toward zebrafish embryos were determined in the present study. In the acute toxicity test, a series of toxic symptoms of embryos were observed, including abnormal spontaneous movement, slow heartbeat, yolk sac oedema, pericardial oedema, spine deformation and hatching inhibition, and 96-h-LC50 (50% lethal concentration) of boscalid toward zebrafish embryos was 2.65 (2.506-2.848)mg/L. From the results of the sub-lethal developmental toxicity test, boscalid was confirmed to have a great impact on development mechanisms of zebrafish embryos. Cell apoptosis in embryos was induced by boscalid with upregulation of genes in the cell apoptosis and an increase of capspase-3 and caspase-9 activity in the present study. Lipid metabolism was affected in embryos due to changes in gene expression and the contents of total triacylglyceride and cholesterol. Melanin synthesis and deposition was caused in embryos due to alterations in related gene expression. Overall, changes in cell apoptosis, lipid metabolism and melanin synthesis and deposition might be responsible for developmental toxicity of boscalid to zebrafish embryos.