Gonad development and vitellogenin production in zebrafish (Danio rerio) exposed to ethinylestradiol and methyltestosterone

The progestin levonorgestrel affects sex differentiation in zebrafish at environmentally relevant concentrations

“…It is interesting that we observed 100% males in the zebrafish exposed to 10 ng/L LNG. Several previous studies have shown that exposure of fish to environmental androgens during their early life-stages could result in male-biased populations (Blázquez et al, 2001;Holbech et al, 2006;Örn et al, 2003). Therefore, our results suggest that LNG is a potent androgen, with strong androgenic activity.…”

“…It is well known that exposure to xenoestrogens or androgens in zebrafish during critical periods of the life cycle can affect sex differentiation, resulting in a change of the sex ratio towards females or males, respectively (Holbech et al, 2006;Örn et al, 2003). As LNG has strong androgenic activity, we hypothesize that LNG may affect sex differentiation during the gonadal differentiation period, which will lead to biased sex ratios of the exposed fish.…”

Ecotoxicological aspects related to the presence of pharmaceuticals in the aquatic environment

“…Concentrations below 1 ng L −1 gave rise to an increased female population and for EE2 concentrations above 3.5 ng L −1 , fish became completely feminized [148]. Concentrations above 1 ng L −1 of EE2 also induced higher vitellogenin plasma lev-els in both males and females [149,150]. Nash et al [151] registered similar findings for zebrafish males by simply performing the assay with 0.5 ng L −1 of EE2.…”

“…Life-long exposure of zebrafish to 5 ng L −1 of EE2 has led to reproductive failure due to the absence of sec-ondary male sex characteristics and normal testes [151]. Exposure of juveniles to estrogen has caused skewed sex ratios in favour of females for concentrations of 1 ng L −1 [150]. Sex reversal was complete at levels of 2 ng L −1 [150].…”

“…Exposure of juveniles to estrogen has caused skewed sex ratios in favour of females for concentrations of 1 ng L −1 [150]. Sex reversal was complete at levels of 2 ng L −1 [150]. Xu et al [152] also exposed zebrafish to EE2 during their period of sex differentiation, show-ing that, after 90 days posthatch, there was already an increase in mortality rate and sex ratio for fish exposed to concentrations of 2 ng L −1 .…”