Effects of copper exposure on the hatching status and antioxidant defense at different developmental stages of embryos and larvae of goldfish Carassius auratus.

This study aims to assess the effects of copper exposure on hatching status and antioxidant defense at different stages of embryos and larvae of goldfish Carassius auratus. In this study, day-old embryos were randomly grouped after fertilization and then exposed to copper concentrations of 0, 0.1, 0.4, 0.7, and 1.0mgL(-1). Copper-exposed fish embryos were sampled every 24h to determine superoxide dismutase (SOD), and catalase (CAT) activities, as well as malondialdehyde (MDA) content. In addition, cumulative mortality and larval deformity were also investigated. The findings showed that cumulative mortality and larval deformity rate increased gradually with copper concentration increase. SOD and CAT activities were inhibited at higher copper concentrations. At a lower concentration (0.1mgL(-1)), SOD activity increased in larvae, whereas CAT activity showed no significant change (p>0.05). MDA, as the lipid peroxidation product, gradually accumulated in embryos and larvae with increasing copper concentration and the extension of exposure time. At 0.4mgL(-1) and more, copper toxicity was shown in embryos and larvae. In conclusion, copper-exposed effects on hatching status and antioxidant defense in C. auratus embryos and larvae showed concentration- and time-dependent patterns. The biochemical parameters in this study can be used as effective indicators for evaluating the responses of copper-exposed fish embryos. In addition, this study demonstrates that 0.4mgL(-1) copper (corresponding to 1mgL(-1) copper sulfate), used to kill parasites in aquaculture, is not safe concentration, because it can result in toxicity to larvae. Therefore, the copper concentration to kill pathogen should be less than 0.4mgL(-1) for C. auratus.