- Tail development
Development of the tail in C. elegans follows distinct sex-specific programs. Upon hatching there is very little morphological distinction between the hermaphrodite and the male C. elegans L1. By the adult stage, the hermaphrodite tail is a tapered whip of hypodermis. By contrast the adult male tale is a complex mating structure that stemmed from sex-specific cell lineages as well as reprogrammed cell fates.
- Male sexual development
The establishment of the sex of a male organism by physical and physiological differentiation through sex-specific developmental pathways leading to a fully fertile male of the species.
- Male mating
Elaborate motor programs are characteristic of C. elegans male mating behavior. Driven by sensory perception males undergo a number of invariant steps allowing the male to locate, confront, and copulate with the hermaphrodite. Studies of C. elegans male mating have elucidated the cellular role of evolutionary conserved polycystins, which has further shed light on their human homologs in autosomal dominant polycystin kidney disease.
- Spermatogenesis
Spermatogenesis is the process of generating functional sperm from an undifferentiated germ cell. In C. elegans, spermatogenesis occurs in both males and hermaphrodites. In both sexes, the germ line initiates spermatogenesis during the L4 larval stage. In the male, spermatogenesis continues throughout adulthood. In the hermaphrodite, however, during the adult stage the germ line ceases spermatogenesis and switches to oogenesis. Sperm made by the hermaphrodite are stored and used for self-fertilization of the hermaphrodite's oocytes. Hermaphrodite sperm differ from male sperm in size with male spermatids being much larger than those of the hermaphrodite. In addition, spermiogenesis is regulated by sex-specific mechanisms. Unlike other sperm-bearing organisms, C. elegans and other nematodes spermatozoa move by a unique crawling mechanism using a single pseudopod. The major sperm protein (MSP), instead of actin, is the main cytoskeletal fiber used in the pseudopod.
- 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.
- Reproduction
A fundamental biological process resulting in the production of offspring. In C. elegans, reproduction can result from self-fertilization within a hermaphrodite or by fertilization by mating of a male and hermaphrodite. In C. elegans, during the fourth larval stage of hermaphrodite development, the germline undergoes spermatogenesis to make functional sperm that are stored in the the gonad. In the adult stage, the germline ceases spermatogenesis and switches to oogenesis to produce oocytes that are fertilized by the previously generated spermatozoa or by spermatozoa deposited into the spermatheca during mating with a male. The embryos produced by self-fertilization are encased in an eggshell and initiate development within the uterus of the hermaphrodite. When they reach about the 30-cell stage, the egg-embryos are laid by the hermaphrodite through a vulva.
- Mechanosensation
Mechanosensation converts mechanical energy into electrical signals allowing an organism to use physical cues from the environment or from internal sensors to affect its behavior. Mechanical stimuli are received through mechanosensory receptor neurons (MRNs). In C. elegans, there are 30 putative MRNs in hermaphrodites while an additional 52 MRNs are found in males. More than 40 of these male-specific MRNs are found in the male tail, hook, post-cloacal sensilla and spicule and are required for male mating. MRNs transmit electrical signals to other neurons through electrical or chemical synapses. MRNs may or may not have ciliated dendrite endings, which is some cases are exposed to the outside. Mechanical stimuli initiate as well as modulate many behaviors of the worm. MRNs allow the worm to respond to light touch, such as stroking with an eyelash as well as harsh touch, such as prodding with a pick.
- Larval development
During post-embryonic development the temporal and spatial regulation of cellular and molecular mechanisms continue past embryogenesis to give rise to a fully functional adult. Post-embryonic development in C. elegans involves progression of the animal through four larval stages. Post-embryonic development involves further limited somatic cell division and cell death to bring the final total to 959 somatic nuclei in the hermaphrodite and 1031 in the male. Other remarkable processes during this period include cell migrations, neuronal rewiring, and adoption of final cell fates. Under conditions of stress, e.g., starvation, reproductive development ceases and the animal switch to a physiologically distinct developmental program to produce the dauer larva.
- Dosage compensation
A mechanism for regulating chromosome-wide gene expression based on the ratio of autosomes to sex chromosomes. In C. elegans, the hermaphrodite is XX with two X chromosomes while the male is X0 with only one X chromosome. Dosage compensation machinery in these nematodes reduces expression of genes on both X chromosomes in the hermaphrodite.
- 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).