Chemosensation
Chemosensation is the process of detecting, processing, and responding to volatile and water-soluble stimuli in the environment. C. elegans has a sophisticated chemosensory system, with much of its nervous system devoted to this process. Detection of these stimuli can result in behavioral outputs such as avoidance of or attraction to the chemical. While physiological responses can include a switch in developmental programs to a dauer stage rather than continuing to reproductive maturity. The amphid (anterior) and phasmid (posterior) chemosensory organs mediate chemosensation. On a cellular level, detection and activation of the chemosensory systems occurs through G-protein coupled receptors (GPCRs), of which different combinations are expressed in each amphid sensory neuron. The combination of GPCRs direct the type of chemical sensed and the response of the animal to the stimulus.