Caenorhabditis is a genus of nematodes which live in bacteria-rich environments like compost piles, decaying dead animals and rotting fruit. The name comes from Greek: caeno- (καινός (caenos) = new, recent); rhabditis = rod-like (ῥάβδος (rhabdos) = rod, wand).

The genus Caenorhabditis contains the noted model organism Caenorhabditis elegans and several other species for which a genome sequence is either available or currently being determined. The two most-studied species in this genus (C. elegans and C. briggsae) are both androdioecious (they have male and hermaphrodite sexes) whereas most other species are gonochoristic (they have male and female sexes).

C. elegans is the type species of the genus. In 1900, Maupas initially named the species Rhabditis elegans, Osche placed it in the subgenus Caenorhabditis in 1952, and in 1955, Dougherty raised Caenorhabditis to the status of genus.

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