The Gut Microbiota’s Effect on Sociability in Fruit Flies

Abstract

Social behaviour is defined as interactions between conspecifics. One facet of it, sociability, involves non-aggression interactions between conspecifics. Little research has investigated the genetics of sociability; more emphasis has been placed on its modulation by the environment. One component of the environment that has been of particular interest is the gut microbiome. Prior research indicates that the gut microbiome likely affects the behaviour of hosts via local manipulation and as an offshoot of metabolic processes, via potential channels including the vagus nerve and the immune system. The effect of the gut microbiome on social behaviour has mostly been investigated using rodent models. Fruit flies would be a useful model, given the simplicity of their gut microbiome and protocols to manipulate to it. There has been insufficient research on gut microbiome modulation of social behaviour in fruit flies (Drosophila melanogaster). We investigated the effects of the gut microbiome on adult fly sociability by generating germ-free wild-type flies and raising them on a germ-free food medium. After housing the flies in mixed-sex groups for 72 hours, we scored their sociability using a sociability assay developed in the Dukas lab at McMaster University. We found that germ-free females were more sociable than control females. A follow-up experiment did not confirm this effect. We postulate that this inconsistency in the results may have been due to reasons such as variation in food quality and atmospheric conditions, or a lack of robustness in the effects of microbes on sociability. Future work in this area would benefit from access to better-regulated microbial work facilities, and should focus on simulating environmental variation in diet and atmospheric conditions to discern its impacts on fly social behaviour.