Neuromuscular Basis of Drosophila larval escape behavior.

When threatened by dangerous or harmful stimuli, animals engage in diverse forms of rapid escape behavior. In Drosophila larvae, escape behavior is characterized by C-shaped bending and lateral rolling, followed by rapid forward crawling. The sensory circuitry that promotes escape has been extensively characterized, but the motor programs underlying escape are unknown. Here, we characterize the neuromuscular basis of escape. We use high-speed, volumetric, Swept Confocally-Aligned Planar Excitation (SCAPE) microscopy to image muscle activity during larval rolling. Unlike the sequential peristaltic muscle contractions from segment to segment that underlie crawling, muscle activity progresses in a circumferential sequence during bending and rolling. Certain muscle subgroups show functional antagonism during bending and rolling. We use EM connectome data to identify premotor to motor connectivity patterns that could drive rolling behavior and test the necessity of specific groups of motor neurons in rolling using neural silencing approaches. Our data reveal body-wide muscle activity patterns and putative premotor circuit organization for escape.