Abstract
The nematode Caenorhabditis elegans is one of ideal model organisms for neurogenetic and behavioral genetic researches, because the structure of its simple nervous system with 302 neurons is well-described and so much genetic information is available. The functions of sensory neurons and the molecular mechanisms of sensory transduction have been elucidated by genetic and behavioral studies. In this review, I will summarize the physiological and molecular basis for chemosensation and chemotactic response of the nematode. The nematode senses many environmental chemicals and integrates the sensory signals within the nervous system to generate chemotactic behavior. Two bilaterally symmetric amphids and phasmids, located on the head and tail of a nematode respectively, are known for chemosensory organs. I will also describe the behavioral plasticity such as associative learning and the regulation mechanism of population density on the chemotaxis.
