Exposure to 17α-ethynylestradiol impairs reproductive functions of both male and female zebrafish (Danio rerio)

In this study, the impact of 17α-ethynylestradiol (EE2) on reproduction in zebrafish (Danio rerio) was evaluated using vitellogenin (Vtg) induction, mortality rate, growth, sex ratio, gonad histology, fecundity, and sperm parameters as endpoints. Two days post-hatch (2 dph) zebrafish were exposed to solvent control or EE2 at 0.4, 2, and 10 ng/l for 3 months. At 21 dph, Vtg mRNA expression was detected only in fish exposed to 10 ng/l EE2. At 90 dph, increased mortality rate and sex ratio (female:male) were observed in fish exposed to 2 and 10 ng/l EE2. A dose-dependent increase in gonads with underdeveloped gametes was observed in fish exposed to EE2. At 180 dph, malformation of the sperm duct and reduced number of spermatozoa were found in fish exposed to 2 ng/l and 10 ng/l EE2. Reduced fecundity and 12 hpf egg viability were found in EE2-exposed males and females. The number of fish with no expressible milt was elevated dose dependently in EE2-exposed males, although no difference in sperm density was found. After a 3-month recovery period, growth and sex ratio were partially recovered. Our findings suggest that EE2 can adversely affect the fecundity, sex differentiation, gametes development, and other reproductive functions of both male and female zebrafish, and some of the toxic effects persist.