Plasticity in expression of fruit fly larval feeding clusters in response to changes in food quality and distribution

Joining a social group entails a range of possible costs and benefits, with the balance of pros and cons potentially dependent on the specific conditions present in the local environment. In the third-instar stage of fruit fly (Drosophila melanogaster) development, individuals may join together into clusters that can increase access to buried food resources, but this collaboration comes with the possible risks of kleptoparasitism or slowed development. Cluster feeding in D. melanogaster larvae has the potential to be a valuable model for studying the dynamics of social and group behaviours, but little is currently known about the plasticity of its expression. In this study, we set out to explore how this collective behaviour might be shaped by the nutritional quality of the environment and/or the spatial distribution of resources by manipulating the nutritional quality of the larval environment and the configuration of available resources. By tracking the timing, frequency, composition, and size of any feeding clusters that subsequently developed, we could better understand the factors that influenced the expression of this social behaviour. We found that cluster expression varied temporally and with the type of resources present in the environment. When possible, larvae formed clusters more frequently to take advantage of otherwise inaccessible resources. The increased clustering patterns were most dramatically manifested as deeper feeding mines. This work expands our understanding of the plastic nature of this collective behaviour, given that discrete environmental changes elicited dynamic changes in larval behaviours.