High-resolution analysis of individual Drosophila melanogaster larvae uncovers individual variability in locomotion and its neurogenetic modulation

Abstract

Neuronally orchestrated muscular movement and locomotion are defining faculties of multicellular animals. Due to its simple brain and genetic accessibility, the larva of the fruit fly Drosophila melanogaster allows one to study these processes at tractable levels of complexity. However, although the faculty of locomotion clearly pertains to the individual, most studies of locomotion in larvae use measurements aggregated across animals, or animals tested one by one, an extravagance for larger-scale analyses. This prevents grasping the inter- and intra-individual variability in locomotion and its neurogenetic determinants. Here, we present the IMBA (individual maggot behaviour analyser) for analysing the behaviour of individual larvae within groups, reliably resolving individual identity across collisions. We use the IMBA to systematically describe the inter- and intra-individual variability in locomotion of wild-type animals, and how the variability is reduced by associative learning. We then report a novel locomotion phenotype of an adhesion GPCR mutant. We further investigated the modulation of locomotion across repeated activations of dopamine neurons in individual animals, and the transient backward locomotion induced by brief optogenetic activation of the brain-descending ‘mooncrawler’ neurons. In summary, the IMBA is an easy-to-use toolbox allowing an unprecedentedly rich view of the behaviour and its variability of individual larvae, with utility in multiple biomedical research contexts.

LarvaTagger: manual and automatic tagging of Drosophila larval behaviour

“…Furthermore, the choice of the number of larvae per behavioural assay represents a trade-off between increasing statistics and minimizing crossing events. Indeed, the larvae have highly deformable bodies and are challenging to properly differentiate and track when they interact while being filmed at low resolutions [recent progress has been made at high resolution ( Thane et al 2023 )]. All the tracking solutions we know of require precise calibration and may fail to detect moving objects with minor variations of experimental parameters.…”

LarvaTagger: Manual and automatic tagging ofDrosophilalarval behaviour

“…Furthermore, the choice of the number of larvae per behavioural assay represents a trade-off between increasing statistics and minimising crossing events. Indeed, the larvae have highly deformable bodies and are challenging to properly differentiate and track when they interact while being filmed at low resolutions (recent progress have been made at high resolution [18]). All the tracking solutions we know of require precise calibration and may fail to detect moving objects with minor variations of experimental parameters.…”