Effects of contraceptive (gestodene) on hatching, embryo development, and reproduction in Oryzias latipes

Pharmaceuticals such as gestodene (GES) enter the environment through inadequately treated wastewater from treatment facilities. GES is an oral contraceptive widely used by women to prevent pregnancy. This study aimed to investigate the effects of GES on hatching, embryo development, and reproduction in Japanese medaka (Oryzias latipes). Although GES did not significantly affect the hatching rate or the number of malformed embryos, it reduced the post-hatching survival rate. GES reduced egg production and adversely affected reproduction. Video observations showed that only male medaka exhibited courtship behavior, indicating that GES inhibited the spawning ability of female medaka. Analyzing the genes associated with female mating receptivity revealed that the expression levels of gnrh1, gnrh2, fshβ, lhβ, kiss1, kiss2, ptgs2, and ptger4b were unchanged. This study is the first to investigate the effects of GES on Japanese medaka.