Sensory regulation of male mating behavior in Caenorhabditis elegans.

C. elegans male mating behavior comprises a series of steps: response to contact with the hermaphrodite, backing along her body, turning around her head or tail, location of the vulva, insertion of the two copulatory spicules into the vulva, and sperm transfer. By ablation of male-specific copulatory structures and their associated neurons, we have identified sensory structures and neurons that participate in each of these steps: the sensory rays mediate response to contact and turning; the hook, the postcloacal sensilla, and the spicules mediate vulva location; the spicules also mediate spicule insertion and regulate sperm transfer. Generally, successful completion of each step places the male in a position to receive a cue for the next step in the pathway. However, the high degree of sensory regulation allows the male to execute some steps independently.