Swine farm wastewater discharge causes masculinization of western mosquitofish
Huang GY et al. in the research group of Professor GG Ying in the Environmental Research Institute, South China Normal University, published a research article “Swine farm wastewater discharge causes masculinization of western mosquitofish (Gambusia affinis)” in Environment International. It is the first time to find that swine farm wastewater could lead to masculinization of fish population.
Natural and synthetic steroid hormones have been detected in swine farm wastewaters (SFWs) and receiving waters. However, little is known on their potential endocrine disrupting effects on fish population in receiving rivers.
Huang et al. investigated the concentrations of androgens and estrogens in the SFWs and the receiving waters. They also analyzed the endocrine disrupting effects of SFWs on wild western mosquitofish (Gambusia affinis) by assessing the sex ratio, secondary sex characteristics and transcriptional expression of genes related to the endocrine system. Chemical analysis showed the maximum concentration of total androgens reached 1380 ng L-1 in the SFWs and 1020 ng L-1 in receiving river waters. A total of 3552 adult G. affinis were collected from the Lianhe River in Guangdong, China, which was heavily impacted by SFWs, before and after the Ban of Swine Farming (BSF) in the river basin. The results showed the presence of male-biased G. affinis populations and masculinized anal fins and hemal spines of females at all contaminated sites prior to BSF. In addition, the transcription of vitellogenin (vtg) was inhibited by SFWs by 99.9% in the females from one sampling site. In contrast, the adverse effects on the females were significantly decreased after BSF. Statistical analyses showed that skewed sex ratios of fish populations, masculinized secondary sex characteristics of females and the decrease of vtg transcripts of females were well correlated with the concentrations of androgens in the receiving waters. The findings from this study suggest that SFW can cause masculinization effects in wild G. affinis populations. Therefore, we need to enforce waste pollution control in order to reduce potential negative impacts on ecosystem.
Reference:
Huang, G.Y., Liang, Y.Q., Liu, Y.S., Shi, W.J., Liu, S.S., Hu, L.X., Xie, L., Ying, G.G. 2019. Swine farm wastewater discharge causes masculinization of western mosquitofish (Gambusia affinis). Environ. Int. 123, 132-140.