Endocrine disrupting effects of domestic wastewater on reproduction, sexual behavior, and gene expression in the brackish medaka Oryzias melastigma

The objective of this study was to investigate the endocrine disrupting effects of domestic wastewater on fish using the brackish medaka Oryzias melastigma as the animal model. Estuarine water samples were collected from Sihchong Creek and Baoli Creek estuaries, Taiwan, in March of 2012 to assess the whole effluent toxicity (WET) of domestic wastewater produced by the local residents and tourists. Chemical analysis detected various pharmaceuticals and personal care products (PPCPs) in the field water samples. Some of these PPCPs are endocrine disrupting chemicals. In the laboratory-based bioassay, breeding pairs were exposed to the water samples (Sihchong, Baoli, and control) for 21 days. Cumulative number of eggs spawned was significantly higher in the Sihchong group. While fish swimming activity was not affected, sexual behavior of the male fish was significantly induced in both Sihchong and Baoli groups. Male and female gonad histology was not affected. Expression level of biomarker genes CYP1A1, HSP70, and VTG was significantly induced in the Sihchong group. This study indicates that the mixture of contaminants contained in the estuarine water may cause endocrine disrupting effects in fish.