Joint dynamics of turning and crawling in the foraging behavior of D. melanogaster larvae

The foraging behavior of the model organism Drosophila melanogaster larva can be coarsely characterized as a sequence of "runs" (forward crawls) and "tumbles" (turns). Yet the precise, posture-scale motions that larvae use to navigate in various environments are yet to be described. We combine flourescence imaging in muscles with markerless keypoint tracking to extract the full range of body deformations which consist of longitudinal and bending dynamics. In the covariance of these deformations we find evidence for separate head dynamics and show that deep body bends are enhanced in environments without strong sensory cues, while correlations between longitudinal deformations are enhanced during chemotaxis, thus supporting goal-directed motion. We analyze larva behavior through short posture sequences and find that forward crawls and turns naturally emerge as longer-time motifs in a Markov dynamics. Further we find that forward motifs occur with a distinct bending bias.