Abstract
Despite the prevalence and research interest of animal personality, its underlying mechanisms are not yet fully understood. Due to the essential role of monoamines in modulating behaviour, we manipulated the monoaminergic systems of Mediterranean field crickets (Gryllus bimaculatus) to explore whether this altered behavioural responses commonly used to describe animal personality. Previous work has shown that both serotonin and dopamine manipulations can alter cricket behaviour, although results differ depending on the drug in focus. Here, we investigate the effect of Fluphenazine, a dopamine antagonist which also interacts with serotonin receptors, on activity, exploration, boldness, and aggression. These results are compared with those of our earlier work that investigated the effect of drugs that more specifically target serotonin or dopamine systems (Fluoxetine and Ropinirole, respectively). Due to limited research on dose-effects of Fluphenazine, we created dose-response curves with concentrations ranging from those measured in surface waters up to human therapeutic doses. We show that compared to control animals, Fluphenazine manipulation resulted in lower levels of both exploration and boldness, but did not affect activity nor aggression. The effect on explorative behaviour contradicts our previous results of serotonin and dopamine manipulations. These results together confirm the causal role of monoamines in explaining variation in behaviour often used to describe animal personality, effects that can be both dose- and behaviour-dependent. Further, our results suggest that previous results assigned specifically to the dopaminergic system, may at least partly be explained by effects of the serotonergic system. Thus, future studies should continue to investigate the explicit underlying roles of specific monoamines in explaining behavioural variation.
Highlights
Animal personality, is widely observed (Gosling, 2001; Carere and Maestripieri, 2013), and can have ecological and evolutionary consequences (Smith and Blumstein, 2008)
Due to the predicted lower dopamine-specificity and different mode of action of Fluphenazine compared to Ropinirole (Meltzer, 2004), we predicted that monoamine manipulation using Fluphenazine would affect our measured behaviours in a more similar way to that of serotonin manipulation than that of manipulation via drugs that manipulate only dopamine levels (Abbey-Lee et al, 2018, 2019)
None of the four behavioural variables measured here correlated strongly with each other
Summary
Animal personality (i.e. consistent among-individual variation in behaviour, Dall et al, 2004; Sih et al, 2004; Reale et al, 2007), is widely observed (Gosling, 2001; Carere and Maestripieri, 2013), and can have ecological and evolutionary consequences (Smith and Blumstein, 2008). We observed that manipulation of dopamine (via manipu lation by Ropinirole, a highly selective dopamine receptor agonist, Kvernmo et al, 2008) did not significantly alter these behaviours This result contradicts other studies that suggest a link be tween behaviour describing personality and the dopaminergic system In the current study, we repeated the methods of our previous work (Abbey-Lee et al, 2018), using different doses of a less selective dopamine receptor antagonist, Fluphenazine (Degen et al, 2000), to again experimentally manipulate the monoaminergic systems of male Mediterranean field crickets. Based on the comparison to our previous work, we predicted to see reduced activity, boldness and aggression in manipulated crickets, and reduced exploration due to the observed link between the dopaminergic system and exploratory behaviour (Kempenaers et al, 2007)
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