Increasingly, studies are revealing that endocrine disrupting chemicals (EDCs) can alter animal behavior. Early life exposure to EDCs may permanently alter phenotypes through to adulthood. In addition, the effects of EDCs may not be isolated to a single generation − offspring may indirectly be impacted, via non-genetic processes. Here, we analyzed the effects of paternal atrazine exposure on behavioral traits (distance moved, exploration, bottomdwelling time, latency to enter the top zone, and interaction with a mirror) and whole-brain mRNA of genes involved in the serotonergic system regulation (slc6a4a, slc6a4b, htr1Aa, htr1B, htr2B) of zebrafish (Danio rerio). F0 male zebraFIsh were exposed to atrazine at 0.3, 3 or 30 part per billion (ppb) during early juvenile development, the behavior of F1 progeny was tested at adulthood, and the effect of 0.3 ppb atrazine treatment on mRNA transcription was quantified. Paternal exposure to atrazine significantly reduced interactions with a mirror (a proxy for aggression) and altered the latency to enter the top zone of a tank in unexposed F1 offspring. Bottom-dwelling time (a proxy for anxiety) also appeared to be somewhat affected, and activity (distance moved) was reduced in the context of aggression. slc6a4a and htr1Aa mRNA transcript levels were found to correlate positively with anxiety levels in controls, but we found that this relationship was disrupted in the 0.3 ppb atrazine treatment group. Overall, paternal atrazine exposure resulted in alterations across a variety of behavioral traits and showed signs of serotonergic system dysregulation, demonstrating intergenerational effects. Further research is needed to explore transgenerational effects on behavior and possible mechanisms underpinning behavioral effects. OPEN ACCESSCitation: Lamb SD, Chia JHZ, Johnson SL (2020) Paternal exposure to a common herbicide alters the behavior and serotonergic system of zebrafish offspring. PLoS ONE 15(4): e0228357. https://doi.

Animal personality is defined as individual variation in behaviour that is consistent over time and/or across contexts. Animal personality is now considered a fundamental aspect in the fields of animal behaviour and behavioural ecology, yet the majority of studies assess repeatability of behaviours over only relatively short time periods (e.g. a week) using just two measures. Understanding whether behavioural traits are repeatable over longer periods is important for the assessment of individual differences in behaviour. Using zebrafish (Danio rerio), we investigated the repeatability of activity and exploratory behaviours, including distance travelled, time spent in the bottom of the arena, stationary time and overall exploration of the novel arena over a 28‐week period, using five intervals. All measures were repeatable over 28 weeks, but the repeatability estimates were much lower when comparing the initial week one and week two behaviours. There were clear sex differences in aspects of activity, with males more active than females. Importantly, our behavioural assays suggest that zebrafish require an initial “tank experience,” prior to the main phenotyping session, to ensure that behaviours being measured are repeatable—these effects are often not considered, but have implications for the many studies that measure behaviour at a single time point only.

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