- Germline development
During germline development germ cells, or reproductive cells, are specified, proliferated, and maintained for the establishment of a germline in the next generation. In C. elegans, germ cells are specified from somatic cells during early embryogenesis. During larval stages, cells of the germline proliferate, undergo meiotic entry, and the germline undergoes sex determination. Gametogenesis, specifically spermatogenesis, begins in late L4 in the hermaphrodite, and switches to oogenesis after the adult molt. Germline proliferation, meiotic development, and gametogenesis continue throughout adulthood.
- 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.
- 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.
- Embryogenesis
The process by which an embryo forms and develops, marking a time of rapid cell proliferation, specification, and differentiation. Embryogenesis in C. elegans takes about fourteen hours at 22 degrees C, starting with fertilization of the oocyte with self-sperm from the hermaphrodite or sperm from a male. During the first two hours, the zygote forms and early cleavages establish the embryonic axes. Somatic and germ-line founder cell fates are also determined. During the next five hours, most cell proliferation completes, the embryo undergoes gastrulation, and cell differentiation and organogenesis begins. Cell differentiation, organogenesis and morphogenesis are completed during the final stage of embryogenesis. The nervous system becomes active and muscles are stimulated during this last stage, resulting in the embryo twitching within its egg shell and eventually hatching as an L1 larva.