Embryonic development and oxidative stress effects in the larvae and adult fish livers of zebrafish (Danio rerio) exposed to the strobilurin fungicides, kresoxim-methyl and pyraclostrobin

Two important strobilurin fungicides, kresoxim-methyl and pyraclostrobin, are widely used globally. Their effects on embryonic development and oxidative stress effects in the larvae and adult fish livers of zebrafish (Danio rerio) were assessed in our study. The hatching, mortality, and teratogenic rates were determined when the eggs of fish were exposed to kresoxim-methyl and pyraclostrobin for 24-144 h postfertilization (hpf). For further study, the effects of kresoxim-methyl and pyraclostrobin on antioxidant enzymes [catalase (CAT), superoxide dismutase (SOD) and peroxidase (POD)], detoxification enzymes [carboxylesterase (CarE) and glutathione S-transferase (GST)] and the malondialdehyde (MDA) content of larval zebrafish (96 h) and male or female adult zebrafish livers (up to 28 d) were evaluated for potential toxicity mechanisms. The study of embryonic development revealed that both kresoxim-methyl and pyraclostrobin caused developmental toxicity (hatching inhibition, mortality, and teratogenic rates) increase with significant concentration- and time-dependent responses, and the 144-h median lethal values (LC50) of kresoxim-methyl and pyraclostrobin were 195.0 and 81.3 mu g L-1, respectively. In the larval zebrafish study, both kresoxim-methyl and pyraclostrobin at the highest concentrations (100 mu g L-1 and 15 mu g L-1, respectively) significantly increased the CAT, POD and CarE activities and MDA content compared with those of the control group (P < 0.05). We further found that oxidative stress effects in adult zebrafish livers caused by long-term kresoxim-methyl and pyraclostrobin exposure differed with time and sex. Regarding the residues in natural waters, the potential adverse effects of kresoxim-methyl and pyraclostrobin would be relatively low for adult zebrafish but must not be overlooked for zebrafish embryos/larvae (hatching impairment). Our results from the detoxification enzyme study also initially indicated that adult zebrafish had a greater detoxification ability than larvae and that males had a greater detoxification ability than females. (c) 2020 Elsevier B.V. All rights reserved.