elegans

Caenorhabditis elegans, often referred to as C. elegans, is a small free-living nematode that has become one of the most studied model organisms in biology. It is native to soil habitats but is widely cultured in laboratories for research.

It belongs to the phylum Nematoda, class Chromadorea, order Rhabditida, family Rhabditidae, genus Caenorhabditis, with the species epithet elegans. The organism is typically studied as C. elegans in scientific literature.

Adults measure about 1 millimeter in length and are transparent, allowing direct observation of internal processes. Reproduction occurs through two sexes: self-fertilizing hermaphrodites and males. Hermaphrodites produce sperm first and then oocytes, enabling selfing, while males arise at low frequency or via cross-fertilization. The life cycle from egg to adult takes roughly three days at 20°C and includes a dauer larval stage that permits survival under adverse conditions.

C. elegans has an invariant cell lineage, and the adult hermaphrodite contains 959 somatic cells (males have 1031). The nervous system of the hermaphrodite comprises 302 neurons, and the complete connectome has been mapped. The genome was one of the first multicellular organisms to be fully sequenced, with about 20,000 protein-coding genes, providing extensive resources for functional genomics and developmental studies.

The species is a foundational model for development, programmed cell death, aging, and neurobiology. It facilitated the discovery and use of RNA interference (RNAi) as a gene function tool and remains central to genetic, genomic, and systems biology research, supported by abundant mutant strains and community resources. C. elegans is routinely cultured on nematode growth medium with Escherichia coli OP50 and is valued for its simplicity, rapid generation time, and broad applicability.