Toxic effects of three strobilurins (trifloxystrobin, azoxystrobin and kresoxim-methyl) on mRNA expression and antioxidant enzymes in grass carp (Ctenopharyngodon idella) juveniles

• Strobilurins may inhibit growth of the fish early life stage.
• The growth-energy-stress-gene expressions are changed.
• Antioxidant enzymes may be damaged.
• Strobilurins may pose a risk to aquatic ecosystems.
• Increase of oxidative stress.

The strobilurins are used widely in the world as effective fungicidal agents to control Asian soybean rust. In this study, the early life stage of grass carp (Ctenopharyngodon idella), which is one of the most important aquaculture species in China, was chosen to measure the acute toxicity of three common strobilurin-derived fungicides (trifloxystrobin (TFS), azoxystrobin (AZ) and kresoxim-methyl (KM)). As endpoints, normal developmental parameters (lethal concentration (LC50) and average heart rate), expression of relative genes, and three antioxidant enzyme activities in the developing juveniles were recorded during a 48 h exposure. The results revealed that values of LC50 were TFS 0.051 (0.046–0.058) mg L−1, AZ 0.549 (0.419–0.771) mg L−1 and KM 0.338 (0.284–0.407) mg L−1 for juveniles. For the potential toxicity mechanisms, these three fungicides increased catalase (CAT) and peroxidase (POD) activity and decreased superoxide dismutase (SOD) activity, significantly inhibited expressions of three growth-related genes (IGF-1, IGF-2 and GHR) and two energy-related-genes (CCK and PYY), and caused pronounced up-regulation a stress-gene (HSP70). The present study demonstrated potential toxic effects of TFS, AZ and KM on the early development of C. idella. Overall, three strobilurins (TFS, AZ and KM) might cause serious damages to the aquatic species; therefore, their pollution supervision in water ecological environment should be strengthened.