2,2′-Dithiobis-pyridine induced reproductive toxicity in male guppy (Poecilia reticulata)

Abstract

Metal pyrithiones (MePTs) are frequently used antifouling biocides in marine coatings. Their main degradation product, 2,2′-dithiobis-pyridine ((PS)2), has been widely detected in seawater and may pose potential ecological risks. In the present study, sexually mature guppies (Poecilia reticulata) were exposed to (PS)2 at concentrations of 0, 20, 200, and 2000 ng/L for 28 days to investigate its reproductive toxicity. The results showed that (PS)2 significantly reduced testosterone (T) levels, spermatogenic cyst number and sperm motility, impeded spermatogenic cell differentiation in male guppies and delayed embryo development in females. These results indicated that (PS)2 could cause reproductive toxicity in guppies. We also examined mRNA expression of indices involved in the hypothalamic–pituitary–gonadal axis and reproductive behaviors. We found that 200 and 2000 ng/L (PS)2 decreased T synthesis by downregulating 17βHSD and CYP17 mRNA levels, and upregulating the mRNA level of CYP19a1a, which converted T to 17β-estradiol. (PS)2 also upregulated GnRH1, FSHβ, LHβ, and LHR mRNA levels, a positive feedback regulation due to the decrease of T levels in male guppies. Furthermore, (PS)2 significantly decreased CYP19a1b mRNA levels in all three exposure groups and thus reduced the display frequency of male guppies. This study was the first to report that (PS)2 could induce reproductive toxicity, which would provide a basis for future assessment of its ecological risk.