Beyond mortality: behavioural disruption and reduced plasticity as sublethal effects of per- and polyfluoroalkyl substances

Environmental pollution represents a major global threat to biodiversity, interfering with a wide range of biological processes and functions. In recent years, behaviour has gained attention as a key focus for detecting the subtle adverse effects of pollution, as pollutants can modify behaviour at both individual and population levels. Per- and polyfluoroalkyl substances (PFAS) are among the most pervasive anthropogenic pollutants. In this study, we analysed the effect of 50-day exposure to ecologically relevant concentrations of two PFAS (namely perfluorooctanoic acid (PFOA) and GenX) on the behaviour of male guppies (Poecilia reticulata) using repeated open field tests, with refuge, under controlled laboratory conditions. We measured the latency to emerge from a shelter, activity levels, and risk-taking behaviour, examining both average behavioural changes and among- and within-individual behavioural variation. While GenX-exposed fish showed no detectable differences compared with controls, PFOA-exposed fish exhibited lower temporal plasticity and higher overall activity levels. These results suggest that ecologically realistic concentrations of PFAS can alter behaviour and patterns of within-individual behavioural variation, potentially impacting individual fitness and population resilience. Our findings highlight the importance of incorporating individual-level analysis in behavioural testing to uncover subtle yet ecologically relevant effects of anthropogenic stressors on animals.