Early-life stage exposure to the antidepressant paroxetine compromises later-life behavioural phenotypes and animal fitness

Intraspecific behavioural variability (e.g., coping styles) ensures an optimal adaptive response to environmental stressors. These individual stress-coping skills are expressed along a fundamental axis of behavioural variation, the bold-shy continuum. Exposure to neuroactive compounds intended for human use, like paroxetine, may affect behavioural phenotypes, through action on evolutionarily conserved neurological pathways found in humans and other species, such as teleost fish, even at low doses. Although paroxetine is prevalent in water systems worldwide at concentrations in the ng/L range there is no available data on its influence on fish coping styles. Accordingly, this study aimed to assess if early exposure (up to 48 hours post fertilisation (hpf)) to PAR environmental levels (0.04 and 0.4 µg/L) may compromise zebrafish's (Danio rerio) bold and shy behavioural phenotypes at later-life stages (larval and juvenile). The obtained data show that both larval and juvenile stages are sensitive to early-life PAR exposure, as differences between bold and shy behavioural profiles were lost at 8dpf (larval stage) and 45dpf (juvenile stage) for basal swimming activity and stress response (e.g. total swimming distance, inactivity time, thigmotactic behaviour, boldness). These results highlight the need for further studies to understand the ecological implications of these behavioural phenotype modifications.