In traditional classifications, a class of hermaphrodite annelid worms that bear only a few bristles (chaetae). Oligochaetes are very abundant in freshwater and terrestrial habitats. The most familiar members of the class are the earthworm (Lumbricus) and the freshwater bloodworm (Tubifex). Molecular studies have revealed that the evolutionary relationships of annelids are more complex than traditional classifications would suggest, and many members of the Oligochaeta are now placed in the clade Sedentaria, along with some polychaetes and the leeches. See annelida.