A novel approach to quantifying inter-individual distance in insects

Abstract

Behaviour involving two or more individuals within the same species is known as social behaviour. Sexual dimorphisms and environmental cues as well as age, experience and social hierarchy shape social behaviour. The study of this complex behaviour, however, has one essential boundary condition: the distance between individuals. Because social signals (e.g. acoustic, visual or olfactory) have limited reach the inter-individual distance is crucial for the correct transmission of such signals. In this study we present a newly developed assay to study group behaviour and inter-individual distance in Drosophila. This assay consists of a circular observation space flanked by two automatic release devices that allow flies to enter individually. By releasing the flies one at a time, the observer can study different features of (intra-)group behaviour with different group compositions. Importantly, the observer can control (manually or through automatisation) the increase of group size over time. Over the last decades insects became more relevant as convenient model organisms to study the neurophysiological and genetic basis of (human) neuro-developmental disorders. Drosophila models are used to study the genetic and neuronal underpinnings of a wide range of neurological disorders. In some cases the studies revealed alterations in social behaviour consistent with descriptions of behavioural symptoms in human disorders. Social behaviours in Drosophila are well-studied and include courtship, mating, aggression and group interactions. This setup will facilitate the analysis of these aspects of group interactions in Drosophila, allowing for a deeper understanding of the neuronal circuits and genetic factors involved in those behaviours.