HYMENOSTOMATIDA

Order 1. HYMENOSTOMATIDA Delage & Hérouard, 1896

Syns. Hymenostom[at]orida,
Hymenostomida,
Hymenostomina

With characteristics of subclass s.s. (above). Well-defined buccal cavity (with rare exception), typically with paroral membrane plus tripartite AZM (or peniculi ± quadrulus); fusiform, explosive trichocysts in one suborder; mostly free-living, fresh-water forms.

['l'hird suborder distinctly different from first two, possibly deserving independent ordinal status.]

With the more conservative characteristics of the order (above). Relatively inconspicuous "UM + AZM" mouthparts, generally, and one family secondarily mouthless; stomatogenesis parakinetal; preoral but no postoral suture; mucocysts common, but no trichocysts or oral nematodesmata; widespread fresh-water microphagous forms (a few edaphic and/or histophagous, and several polymorphic with carnivorous macrostome stage) plus some symbiotic species, latter (whether facultative or obligate forms) associated mainly with invertebrate hosts. Suborder (1) Tetrahymenina Fauré-Fremiet in Corliss, 1956

Oral ciliature deep in buccal caviry, complex in conformation and comportment, with "watchglass organelle" (often accompanied by pigment mass) characteristically in viciniry; stomatogenesis parakinetal, regularly with oral replacement of parental mouthparts; preoral suture present, postoral less distinct; body size large, conspicuous in trophont-tomont stage; polymorphic life cycle, including cysts and palintomic reproduction; histophagous forms, generally feeding on moribund or wounded fresh-water invertebrates, though several species attack healthy fishes (marine as well as fresh-water) to host's eventual detriment. Suborder (2) Ophryoglenina Canella, 1964

Peniculi of oral ciliature deep in buccal caviry (itself sometimes preceded by oral-area depression or groove, the prebuccal caviry); stomatogenesis buccokinetal; distinct pre- and postoral sutures; spindle trichocysts and nematodesmata, but not mucocysts, of common occurrence; many species with endosymbiotic algae or bacteria; sizable but monomorphic, generally microphagous, forms, often without cysts; widely distributed, predominantly in fresh-water habitats. Suborder (3) Peniculina Fauré-Fremiet in Corliss, 1956

With the more conservative characteristics of the order (above). Relatively inconspicuous "UM + AZM" mouthparts, generally, and one family secondarily mouthless; stomatogenesis parakinetal; preoral but no postoral suture; mucocysts common, but no trichocysts or oral nematodesmata; widespread fresh-water microphagous forms (a few edaphic and/or histophagous, and several polymorphic with carnivorous macrostome stage) plus some symbiotic species, latter (whether facultative or obligate forms) associated mainly with invertebrate hosts.	*Suborder (1) Tetrahymenina* Fauré-Fremiet in Corliss, 1956**
Oral ciliature deep in buccal caviry, complex in conformation and comportment, with "watchglass organelle" (often accompanied by pigment mass) characteristically in viciniry; stomatogenesis parakinetal, regularly with oral replacement of parental mouthparts; preoral suture present, postoral less distinct; body size large, conspicuous in trophont-tomont stage; polymorphic life cycle, including cysts and palintomic reproduction; histophagous forms, generally feeding on moribund or wounded fresh-water invertebrates, though several species attack healthy fishes (marine as well as fresh-water) to host's eventual detriment.	*Suborder (2) Ophryoglenina* Canella, 1964**
Peniculi of oral ciliature deep in buccal caviry (itself sometimes preceded by oral-area depression or groove, the prebuccal caviry); stomatogenesis buccokinetal; distinct pre- and postoral sutures; spindle trichocysts and nematodesmata, but not mucocysts, of common occurrence; many species with endosymbiotic algae or bacteria; sizable but monomorphic, generally microphagous, forms, often without cysts; widely distributed, predominantly in fresh-water habitats.	*Suborder (3) Peniculina* Fauré-Fremiet in Corliss, 1956**