- Ray development
C. elegans male tail contains four types of male-specific sensilla, the most prominent of which are the rays. These 18 sensory rays convey mechano- and chemosensory information critical to male mating. Each ray is composed of three cells: RnA: A-type sensory neuron; RnB: B-type sensory neuron; and Rnst: ray structural cell, which are derived from one neuroblast, the ray precursor cell called Rn. Each ray is morphologically and molecularly distinct from each other. Most all ray identity follows a determinate cell lineage model where cell identity is established based on the pattern of cell division; ray 5 does require external cues from a TGF-beta signalling pathway to adopt its final fate.
- Muscular system development and organization
The coordinated specification and functional assemblage of cells and tissues into the contractile organ system in the animal. C. elegans muscles are of two types: single sarcomere with focal attachment points at the ends (alimentary system and sex muscles) and obliquely striated muscles with many sarcomeres and no one substantial focal attachment point (body-wall muscles). Components of C. elegans muscles are similar to other animals and include heavy and light-chain myosin, actin, tropomyosin, troponin-like proteins, and paramyosin. Unlike other muscle systems, C. elegans muscles send neuron-like processes to neuropils that contain motor neuron axons rather than motor neurons sending axons to innervate the muscle. Contractile tissue is found throughout C. elegans and is required for locomotion (body wall muscle), eating (pharyngeal muscle), egg laying (vulval and uterine muscles, and gonad sheath), male mating (male tail muscles), and defecation (enteric muscles).
- Neurotransmission
Neurons communicate across synaptic junctions with target cells, such as neurons, muscles, or specialized secretory cells through chemical messengers that are released from the neuron and bind to and activate receptors on the target cell. Pre-synaptic release of neurotransmitters can be evoked, such as through mechanical or chemical stimulation, as well as can occur spontaneously at a low rate. Depending on the neurotransmitter released and or the receptors of the post-synaptic cell, the activation of receptors can trigger excitatory or inhibitory actions in the target cell. These neuronal communications can also result in short term post-synapatic cellular changes to the membrane potential or can cause the activation of signaling cascades, resulting in longer term changes in the cell.
- 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.
- Olfaction
Volatile organic molecules are sensed through olfaction. C. elegans can distinguish and respond to many volatile odorants through attractive or repulsive chemotactic behaviors. In some instances volatile compounds can induce both behaviors depending on its concentration. Olfaction studies in C. elegans has revealed a complex sensory system where only three types of neurons (AWC, AWA, and AWB) have been found to be responsible for processing over seven classes of volatile odorants, including alcohols, ketones, organic acids, sulfhydrals, and heterocyclic compounds. Detailed study of the molecular machinery behind odor reception has shown that each neuron controls a particular attractive or repulsive behavioral response, for example, AWC controls attractive chemotaxis responses and AWB controls repulsive chemotaxis responses. One distinguishing feature of C. elegans sensory system is that the sensory neurons are polymodal in their stimulus detecting ablility; that is, individual neurons in C. elegans express multiple odorant receptors allowing multiple sensory functions, whereas vertebrate neurons express a single receptor limiting their function to detecting a single odorant.