Sensory regulation of male mating behavior in caenorhabditis elegans

Abstract

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.

The proximate determinants of sex ratio in C. elegans populations

“…For example, high temperatures promote X non-disjunction (Hodgkin, 1983) and high population densities may promote male mating. Likewise, male reproductive efficiency may be influenced by such genetically controlled traits as copulatory plug formation (Hodgkin & Doniach, 1997), aggregation behaviour (de Bono & Bargmann, 1998), ability of males to obtain copulations (Liu & Sternberg, 1995;Emmons & Sternberg, 1997) and rate of production and size of sperm and oocytes (Hodgkin & Barnes, 1991). Furthermore, the influence of stochastic events on male frequency and outcrossing rates may be particularly important when the predicted sex ratio is so low.…”

Generation and modulation of chemosensory behaviors in C. elegans

“…For the sake of brevity, I will concentrate solely on these behaviors in the hermaphrodite. I refer the reader to several excellent publications and references therein addressing C. elegans male chemosensory behaviors [1][2][3][4][5][6].…”

Genetic basis of male sexual behavior

“…Many of these genes affect other aspects of sensory function or behavior (Hodgkin, 1983;Emmons and Sternberg, 1997). For example, consistent with the known role of ciliated neurons in the male genital structure (Liu and Sternberg, 1995), mutations that result in a general sensory defect because of defects in the cilia of sensory neurons are defective in male copulation (Barr and Sternberg, 1999). Several mutations that affect steps of male copulation more specifically without significant general defects have been isolated (some are termed cod genes, for copulation defective).…”

“…Copulatory behavior is evoked when sensory neurons in the tail detect contact with the hermaphrodite. Such contact initiates a stereotyped series of behavioral steps that lead up to insertion of the male's spicules into the hermaphrodite vulva followed by ejaculation (Loer and Kenyon, 1993;Liu and Sternberg, 1995;Emmons and Sternberg, 1997). Little or no reciprocal behavior is apparent on the part of the hermaphrodite.…”

“…Little or no reciprocal behavior is apparent on the part of the hermaphrodite. The roles played by male-specific tail sensory neurons, interneurons, and motor neurons in each of these steps were determined by examining male behavior after individual cells or subsets of cells were eliminated by laser microbeam ablation (Loer and Kenyon, 1993;Liu and Sternberg, 1995;J. Sulston, personal communication).…”