This class is represented by a single genus of rotifers, which exist as commensal organisms of marine crustaceans. Eggs are haploid, and require fertilisation in order to develop into male or female adults. This speciose class of rotifers is characterised by the presence of two trochal discs. They are active components of the freshwater zoofauna, and move by swimming or crawling. The body is capable of a considerable degree of extension and retraction.
Males are unknown, all reproduction occurring by parthenogenesis.
As the name suggests, this class of organisms is characterised by the presence of a single ovary, and the production of both mictic and amictic eggs. The class is divided into a number of orders. This order contains the vast majority of rotiferan species. These are barrel-shaped, swimming animals that may have a protective lorica surrounding the trunk. The Floculariacea include sessile tube-dwelling forms, and active swimming species in which the foot has entirely degenerated.