Several attractive features of C. elegans biology have contributed its choice as a model organism for the study of genetics, developmental biology, neurobiology, cell biology and behavior. It is easy to maintain in the laboratory, growing quickly on a bacterial lawn grown on an agar plate. Its small size (about 1.3 mm in length and 80 microns in diameter), invariant anatomy and transparent body have made it possible to describe the complete cell lineage from the single cell embryo to all 959 somatic cells in the adult and all the connections between nerve cells.
C. elegans has a short generation time, going from the single-cell egg to an adult in 3.5 days. The embryo hatches and goes through four larval stages before becoming a mature adult. Each larval stage looks similar to the adult, only smaller. C. elegans can adapt an alternative life form, call a dauer larva, in response to overcrowding or the absence of adequate food supply. This dauer larva can remain viable for as long as three months while it roams around in search of food. It is this dauer larvae that is the most common form of C. elegans found in the wild.
The adult is a hermaphrodite, meaning it is both a male and female. When it first becomes and adult it is a male, which produces sperm that it then stores. Next, it becomes a female and produces eggs, which are then fertilized by the stored sperm.
The genome is small compared to humans (about 30 times smaller), yet it encodes over 22,000 proteins, only slightly fewer than humans. About 35% of C. elegans genes are closely related to human genes.
Although the first published description of C. elegans was in 1900 by E. Maupus in the Archives de Zoologie Experimentale et Generale (8: 463-624), it did not become a commonly used as an experimental system until Sydney Brenner's description of its genetics in 1974.
Caenorhabditis elegans is a small, free-living, round worm found in nutrient- and microorganism-rich habitats such as in compost, mushroom beds and garden soil where it feeds on bacteria and probably other microorganisms. Bristol, the most commonly used strain of C. elegans, was isolated from mushroom compost in Bristol, England. Other strains have been isolated from soil and moist environments in temperate regions around the world. It has been found in association with other closely-related Caenorhabditis species, C. briggsae and C. remanei, as well as snails, slugs, millipedes, mites and pill bugs. The association with these non-nematodes may be as a means of transportation to a new food source.
The complete sequence of all 100,269,912 bases was finished in 2002, making it the first genome of a multi-cellular eukaryote in which every base is known. It is high-quality sequence with an estimated error rate of less than 1 in 100,000. The sequence was produced jointly by the Sanger Institute in Hinxton, England and the McDonnell Genome Institute in St. Louis. Funding for the project was provided to the McDonnell Genome Institute by The National Human Genome Research Institute (NHGRI), National Institutes of Health (NIH).