Phthalate Exposure Influences Mating Behaviour and Sperm Morphology in an Aquatic Ecotoxicology Model System

Abstract

Phthalates are a group of chemicals used to make plastics more durable, found in applications from cosmetics, lubricating oils, and flooring to soap, shampoo, and hairspray. Phthalates are also now known to be endocrine disruptors with connections to adverse reproductive outcomes in animals, including humans. Here, we evaluate the potential effects of a widely used phthalate ester, dimethyl phthalate (DMP), on male reproduction in a freshwater snail. DMP is found in industrial applications like solid rocket propellant as well as consumer products such as insect repellents and plastics. Although there is some evidence that DMP negatively affects reproduction, especially in females, we still know very little about potential DMP effects on males. We addressed this important knowledge gap by testing the effects of DMP on Potamopyrgus antipodarum, a prosobranch snail native to New Zealand. These snails are very sensitive to water conditions and environmental chemicals, including endocrine-disrupting compounds, and are thus rising in prominence as water-quality sentinels and ecotoxicology models. We exposed experimental groups of male P. antipodarum to one of three different concentrations of DMP and characterized mating behaviour and sperm morphology as a function of DMP exposure. Differences in these traits were primarily observed between the males in the control versus the high (10−6 M) DMP concentration group. As DMP exposure levels increased, we found that mating frequency ultimately decreased by more than 69% and that sperm morphology was increasingly altered relative to control males. Altogether, study outcomes suggest DMP exposure in male animals could have negative effects on reproduction, with particular relevance in aquatic and marine environments that are especially likely to harbour leached endocrine-disrupting chemicals.