Social experience and the establishment of behavioural syndromes - novel insights from crickets into the role of serotonin in aggression, “personality” and depression-like phenomena

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Recently it has become recognised that individual animals of the same species, including many invertebrates, show consistent difference in their behaviour (often referred to as animal personality). Little is known, however, how such inter-individual behavioural differences arise. Our recently published and preliminary work on male crickets reveals that social experience plays a decisive role. As in many animals, crickets that win a fight against a conspecific become hyper-aggressive, while those that lose become submissive, but these changes are short lived (20 min and 3 h). However, as in mammals, multiple defeats (chronic social defeat) also lead to longer term suppression of aggression in crickets (>24 h, possibly life-long). Moreover, the winning and losing experiences lead to long-term changes in general motility, exploratory behaviour and the motor response to tactile stimulation. We have already shown in several papers that the hyper-aggressiveness of winners is mediated by the amine octopamine, and that loser depression results from activation of the nitric oxide signalling pathway. We now aim to investigate t https://de.wiktionary.org/wiki/submissiv he role of such neuromodulators in determining long term changes in behaviour resulting from aggressive experience. Preliminary work indicates that chronic social defeat induces long term depression of aggression coupled with depressed exploratory behaviour via the combined action of nitric oxide and serotonin. This is a rare insight into the natural behavioural role of serotonin in aggression, which is currently not understood in invertebrates or mammals. In mammals, including humans, chronic social defeat is a major stressor that induces depression like symptoms, but the underlying proximate mechanisms are unclear. Thus, our work not only has the potential to unveil “personality” in a model invertebrate as a form of experience dependent plasticity mediated by neuromodulators, it may also offer novel insights into the role of serotonin in depression-like phenomena.