Distinct motor programs can be coupled to enrich and refine the repertoire of behavior dynamics. However, mechanisms underlying such coupling are poorly understood. The defecation motor program (DMP) of C. elegans is composed of a succession of body contraction and expulsion steps, performed repeatedly with a period of 50-60 sec. Using precise automatic detection of contractions, we show that avoidance-like locomotion dynamics are executed in tandem with the DMP cycle. Moreover, the two motor programs co-reset and co-terminate in response to external stimuli or developmental events. We found that calcium waves in the intestine, known to drive the DMP cycle, drove the avoidance-like behavior. Proton signaling, known to regulate the DMP, also played a role in establishing the appropriate locomotion dynamics during the cycle. Surprisingly, interneurons that were specifically associated with reversals were essential for DMP anterior body contractions and expulsions. Our data suggests that a triggering event, 10 seconds prior to the posterior body contraction, may synchronize avoidance-like locomotion with the DMP cycle. This study provides the first example in C. elegans of two multi-step motor programs being executed concurrently and in synchrony, as well as of intestinal driven directed locomotion. .
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