Rhabditids

Rhabditids are a family of nematodes in the phylum Nematoda, order Rhabditida, commonly referred to as rhabditid nematodes. The best-known genus is Caenorhabditis, which includes the model organism Caenorhabditis elegans. Rhabditidae comprises a diverse group of free-living nematodes that inhabit soil, leaf litter, and freshwater, feeding primarily on bacteria.

Most rhabditids are free-living microbivores. They occur in soil, compost, rotting vegetation, and aquatic sediments, where they help decompose organic matter. Some species associate with plants or insects, and a few lineages have become opportunistic or obligate parasites of invertebrates or vertebrates, though this is not typical of the family as a whole.

The family includes several genera beyond Caenorhabditis, such as Rhabditis. Members are studied for basic biology, genetics, and development, with C. elegans serving as the best-known model organism. Rhabditids provide insights into nematode evolution, sensory and neural function, and host–microbe interactions.

Life cycles are generally direct; eggs hatch into larval stages (L1 to L4) before becoming adults. Many rhabditids, especially Caenorhabditis species, exhibit a dauer larva stage as a response to environmental stress. Reproduction ranges from self-fertilizing hermaphrodites to gonochoristic populations depending on the lineage.

Taxonomically, Rhabditidae is a family within Rhabditida. Identification relies on a combination of morphological traits and molecular data, including ribosomal RNA gene sequences. The taxonomy of nematodes is subject to revision as new molecular analyses refine relationships among genera.