Caenorhabditis elegans (C. elegans) is a free-living nematode (a roundworm), about 1 mm in length, which lives in a temperate soil environment. Research into the molecular and developmental biology of C. elegans began in 1965 by Sydney Brenner. C. elegans are nematodes (roundworms). They are vermiform, bilateral in symmetry, with a cuticle integument, no segmentations, with four main epidermal cords and a fluid filled pseudocoelomate cavity. They also have an organ system and a closed circulatory system. They feed on microorganisms such as Escherichia coli bacteria. C. elegans has a male and hermaphrodite sex. The basic anatomy of C. elegans includues a mouth, pharynx, intestine, gonad, and collagenous cuticle. Males have a single-lobbed gonad, vas deferens, and a tail specialized for mating. Hermaphrodites have two ovaries, oviducts, spermatheca, and a single uterus.
A basic description of the organisms’ life cycle is that C. elegans eggs are laid by the hermaphrodite. After hatching, they pass through four larval stages (L1-L4). When crowded or in the absence of food, C. elegans can enter an alternative third larval stage called dauer. Dauers are stress resistant and do not age. Hermaphrodites produce sperm during the L4 stage, and lay eggs as adults. The male can inseminate the hermaphrodite, which will use male sperm preferentially. The average life span of the laboratory strain of C. elegans at 20°C is about 2-3 weeks, and the generation time is only a few days.
C. elegans are used as a model organism. They have the advantage of being cheap and easy to maintain in the laboratory. C. elegans have been especially useful for studying cellular differentiation, and was the first animal to have its genome completely sequenced. The C. elegans genome contains more than 19,000 genes and approximately 100 million base pairs. This organism is the subject of a proposal which involves cataloguing its glycome.
It has the advantage of being a multicellular eukaryotic organism which is simple enough to be studied in great detail. The developmental fate of all of its 959 somatic cells has been mapped out, which are left from the original 1090 cells, after 131 are eliminated by apoptosis. In addition, C. elegans is one of the simplest organisms with a nervous system. Research has explored the neural mechanisms responsible for two of C. elegans more interesting behaviors: chemotaxis and thermotaxis.