Reproduction Abstracts

Over the last 30 years concerns have risen about the potential for environmental chemicals to cause reproductive effects on wildlife via disruption of endocrine signaling pathways. There are now hundreds of chemicals known to disrupt the endocrine system and a wide range of examples of adverse effects on wildlife, including the feminisation of fish in UK rivers, egg shell thinning in birds, demasculinisation of reptiles and imposex in mollusks.

The aquatic environment acts as a sink for contaminants, and this, together with the increased production of existing and of novel chemicals, results in increased risk of exposure for aquatic organisms, including to reproductive toxicants. There is a significant lack of understanding of the global mechanisms of toxicity of environmental chemicals, alone or in combination with other stressors. This knowledge is essential to build predictive adverse outcome pathways that can support effective management strategies to protect populations at risk.

We have employed transcriptomics to investigate the mechanisms of toxicity of a range of endocrine disrupting chemicals potentially impacting on fish populations, including natural oestrogens and pesticides. We identified conserved and novel pathways of effect for a range of chemicals of interest, including the suppression of cholesterol biosynthesis by linuron, a pesticide commonly found in the aquatic environment. We also demonstrated that Bisphenol A, a component of plastics with weak oestrogenic activity, caused reproductive toxicity in breeding zebrafish, decreased dnmt1 transcription, and reduced global DNA methylation, as well as inducing changes in the promoter methylation and transcription of genes regulating reproduction. Together, these datasets are helping to build a more comprehensive understanding of the molecular mechanisms of effect of chemicals with suspected endocrine activity. These data are supporting the development of adverse outcome pathways to be used in the management of chemical pollution, in order to protect wildlife and human health.