Long-Term Exposure to Environmental Concentrations of Azoxystrobin Delays Sexual Development and Alters Reproduction in Zebrafish (Danio rerio)

The strobilurin fungicide azoxystrobin (AZO) can induce adverse effects in aquatic organisms, but data are lacking on endpoints associated with sexual development and reproduction following chronic exposure to AZO. In this study, zebrafish embryos (F0) at 2-4 h postfertilization (hpf) were exposed to 0.2, 2.0, and 20.0 mu g/L AZO until 120 d postfertilization (dpf). Decreased male ratio and increased intersex ratio were observed by 20.0 mu g/L AZO at 42 and 60 dpf, but this effect disappeared at 120 dpf. AZO at 20.0 mu g/L inhibited growth, retarded gonadal development, and disrupted sex hormone and vitellogenin in females at 60 and 120 dpf and in males at 42, 60, and 120 dpf. These effects were associated with altered expression of cyp19a, cyp19b, hsd3b, hsd17b, vtg1, and vtg2. Exposure to 2.0 mu g/L AZO altered mRNA levels of these transcripts in females at 120 dpf and in males at 60 and 120 dpf. Reproduction ability was reduced by 20.0 mu g/L AZO at 120 dpf. Developmental defects were observed after F1 embryos from exposed parents of 20.0 mu g/L were reared in AZO-free water at 96 hpf. Overall, these data provide new understanding of fish sexual development and reproduction following chronic exposures to AZO.