Embryonic exposure to water accommodated fraction of crude oil inhibits reproductive capability in adult female marine medaka (Oryzias melastigma)

Abstract

The water accommodated fraction (WAF) of spilled crude oil is a severe threat to the health of marine fish. This study was conducted to investigate the effects of short-term embryonic exposure to the WAF on the ovarian development and reproductive capability of F0 adult female marine medaka (Oryzias melastigma). Following embryonic exposure to the WAF with nominal total petroleum hydrocarbon concentrations of 0.5, 5, 50, and 500 μg/L for 7 days, the number of spawned eggs and gonadosomatic indices of F0 adult females were significantly reduced at 130 days postfertilization. In these F0 adult females, the proportion of mature oocytes was significantly lower, the level of 17β-estradiol was lower, and the level of testosterone was greater than those in control group. The mRNA levels of the follicle-stimulating hormone β subunit, luteinizing hormone β subunit, cytochrome P450 aromatase 19b, estrogen receptor α and β, and androgen receptor α and β genes were upregulated, while the mRNA level of the salmon-type gonadotropin-releasing hormone was downregulated in F0 adult females exposed to the WAF during the embryonic stage. Additionally, the methylation level of vitellogenin (vtg) in F0 adult females was significantly elevated, this might have, in turn, downregulated the mRNA level of vtg. The mortality rate of the unexposed F1 embryos was significantly increased and the hatching success was significantly reduced. These results collectively indicated the necessity of incorporating and evaluating the effects of short-term early-life exposure to crude oil in the assessment of risks to the reproductive health of marine fish.