monocystidae monocystidae the monocystidae are a family of parasitic alveolates in the phylum apicomplexa. monocystidae scientific classification domain: eukaryota (unranked): sar (unranked): alveolata phylum: apicomplexa class: conoidasida subclass: gregarinasina order: eugregarinorida suborder: aseptatorina family: monocystidae subfamilies monocystinae oligochaetocystinae rhynchocystinae stomatophorinae zygocystinae taxonomy there are five subfamilies in this family: monocystinae, oligochaetocystinae, rhynchocystinae, stomatophorinae and zygocystinae. history this family was created by bütschli in 1882. description the hosts of the species in this family are usually oligochaetes. the species in this family generally infect the coelom of their hosts. the gamonts are spherical to cylindrical. the anterior end is little differentiated if at all. the oocysts are biconical or boat-shaped.