Abstract/Summary

Microplastics are pollutants present throughout the food chain in terrestrial and aquatic ecosystems. Microplastic exposure causes increased oxidative stress, inflammation, and tissue damage. However, microplastics also impact oestrogenic and androgenic signalling, suggesting that microplastic treatment may impact hormonally-regulated processes, including social behaviours. Despite this, there is a lack of studies linking altered hormonal signalling and hormonally-regulated behaviour changes due to microplastic treatment. This study uses Caenorhabditis elegans to investigate the effects of microplastic treatment on parental and male mating behaviours with a focus on the potential role of the putative androgen receptor, NHR-69, and the putative oestrogen receptor, NHR-14, to understand whether disruption occurs via signalling through these receptors. C. elegans is genetically traceable, possesses conserved hormonal pathways, and presents established social behaviours, making it an ideal experimental system to address microplastic toxicity on social behaviours. This research developed a method of scoring male mating behaviour to gain an in-depth understanding of the specific effects of PS-MP treatment on the mating process. While microplastic treatment caused defects in male mating behaviour, specifically in contact response behaviour and spicule insertion, C. elegans lacking NHR-69 signalling did not show these changes upon PS-MP treatment, suggesting that microplastics may act via the NHR-69-regulated androgenic signalling pathway to disrupt male mating behaviour. In contrast, microplastic treatment of C. elegans males with impaired NHR-14 signalling led to exacerbated microplastic toxicity, measured by a reduction in mating stages performed after scanning behaviour, indicating that microplastics did not impair mating behaviour via this receptor. This study showed that NHR-14 signalling regulates parental behaviours. However, the impacts of microplastics on parental behaviours via this receptor are still unclear. This study highlights the complexity of microplastic interactions with hormonal signalling pathways and outlines the need for further research to unravel the underlying mechanisms.