C. elegans male mating behavior involves multiple steps, including response to the hermaphrodite, backing along her body, turning via a deep ventral bend at the end of her body, vulva location, spicule insertion, and sperm transfer. The male must integrate multiple signals and behave according to the movements of the disinterested, otherwise self-fertilizing hermaphrodite. Vulva location requires input from three sensilla: the hook, the post-cloacal sensilla (p.c.s.), and the spicules (1). The step of vulva location is complex: neuronal circuitry is partially redundant and this functional overlap allows for behavioral adaptation. Vulva location behavior is an excellent model system to dissect neuronal redundancy and behavioral plasticity. By screening for copulation defective (Cod) mutants, several vulva location mutants have been isolated. However, none exhibit severe behavioral or mating efficiency defects. As different sensory pathways appear to be affected in
cod-13(
sy420)III and
cod-12(
sy419)II, we are analyzing these mutants at genetic and cellular (via laser ablations) levels.
sy420 most closely resembles hook-ablation (passes the vulva frequently) while
sy419 mimics p.c.s.-ablation (locates but easily loses the vulva).
sy420 maps to the interval defined by
dpy-17 lon-1. Hook-ablated
sy419 males behave distinctly from hook-ablated wild-type males. Hook-minus wild-type males pass the vulva and circle the hermaphrodite for several minutes before initiating a slow search that requires the p.c.s. and spicules (1). Hookless
sy419 males exhibit a constitutive vulva location behavior involving spicule protraction at random positions along the hermaphrodite's body often coupled with premature sperm release. These behaviors in
sy419 are vulva-dependent but uterus-independent, suggesting a possible defect in sensory feedback regulation. Combination ablations are being performed to determine which neurons are required for this aberrant behavior. Vulva location Cod mutants may affect partially redundant genes and a synergistic Cod phenotype may be produced by two mutations. Since hook ablation augments the behavioral defects of a
sy419 male,
sy419 may provide a sensitive background to obtain mutants with hook-like defects. (1) Neuron (1995) 4: 79-89.