Claim: The hosts of the species, which generally infect the coelom of their hosts, in Monocystidae family are usually oligochetes (a subclass of animals in the phylum Annelida).
Evidence: The hosts of the species in this family are usually oligochetes. The species in this family generally infect the coelom of their hosts. Oligochaeta (/ˌɒlɪɡəˈkiːtə, -ɡoʊ-/) is a subclass of animals in the phylum Annelida, which is made up of many types of aquatic and terrestrial worms, including all of the various earthworms. The Monocystidae are a family of parasitic alveolates in the phylum Apicomplexa.