Meiotic maturation

During female gamete production oocytes arrest during the diplotene stage of meiosis I before completing diakinesis and moving into meiosis II. In response to hormones, oocytes resume and complete meiosis to produce the final mature gametes. In C. elegans, meiotic maturation is triggered by major sperm protein through G-alpha-S-adenylate cyclase - protein kinase A (PKA) signaling and soma-to-germline communication.

Foraging

C. elegans exhibits a number of behaviors that influence its ability to find food. The act of foraging proceeds as an alteration of two behavioral states, roaming and dwelling. These states depend on sensory input, as mutations that affect cilia formation alter the time spent in one state or the other. Nose deflection is another characteristic foraging behavior. In this case, the rapid movement of the nose tip from side to side has been shown to require GABAergic RME neurons. Studies of C. elegans isolates also demonstrate a social aspect to foraging, which is due to natural variations in npr-1, an NPY G-protein-coupled receptor family.

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.

Programmed cell death

Programmed cell death (PCD), or apoptosis, is an integral component of C. elegans development. During development, 131 cells are fated to die by apoptosis. PCD is easily observed with Nomarski optics in the C. elegans embryo; the nucleus of the apoptotic cell becomes refractile, resembling a flat button, making C. elegans an easy model for following apoptotic cell death. PCD in C. elegans can be divided into three main phases (with participating genes): specification of which cells should live or die (ces-1, ces-2, in general); activation of the cell killing machinery (egl-1, ced-9, ced-4 and ced-3); and an execution phase where the dying cell is dismantled and removed through phagocytosis (ced-1,-2,-5,-6,-7,-10 and-12), which occurs in concert with apoptotic DNA degradation (cps-6, nuc-1). Molecular and biochemical studies in C. elegans revealed programmed cell death mechanisms conserved in humans. The regulatory pathway that controls cell death is composed of conserved cell death activators and inhibitors: EGL-1 and BH3-domain-only proteins, CED-9 and Bcl-2, CED-4 and Apaf-1, and CED-3 and caspases, in nematodes and mammals, respectively. Further the degradation of chromosomal DNA involves a mitochondrial proapoptotic endonuclease: endonuclease G (EndoG), and AIF in mammals and their orthologs CPS-6 and WAH-1 in worms.