» For the plant genus from the sunflower family (Asteraceae), see Oligochaeta (plant). Oligochaeta (singular Oligochaete, ) is a subclass in the biological phylum Annelida and includes various earthworms. Specifically, it contains the terrestrial megadrile earthworms (some of which are semi- or fully aquatic), and freshwater or semi-terrestrial microdrile forms including the tubificids, pot worms and ice worms (Enchytraeidae), blackworms (Lumbriculidae) and several interstitial marine worms. Wi… (More on Oligochaeta)