Sessilina

Suborder (1) Sessilina Kahl, 1933

Syns. Asrylozoina,
Loricina,
Natantina,
Scyphidiina,
Sedentaria,
Sessilia,
Sessili[i]da,
Srylophorina,
Thigmodiscina;
Aloricata + Loricata

Sedentary or sessile (adults), commonly stalked (or with inconspicuous adhesive disc), with a few species secondarily mobile; many produce arboroid colonies; some entire groups loricate; mucocysts and pellicular pores universal; adults generally filter-feeding bactivores (larval stage mouthless); widely ranging habitats (fresh-water, brackish, marine), with animate substrata involving metazoa from many phyla (major exception: echinoderms); a few species live as endozoic forms.

With contractile stalk; all species colonial except in two genera (Haplocaulus, Vorticella); zooids not independently contractile among colonial forms (except in Carchesium); species all attached - to inanimate objects, plants, rotifers, crustaceans (amphipods, decapods, etc.), even turtles, etc. - in various fresh-water and marine habitats. Family VORTICELLIDAE Ehrenberg, 1838

Stalkless, mobile, planktonic forms, with one or two rigid caudal bristles; organisms resemble zooids of Vorticella broken away from stalk; mature form swims with apical pole forward, telotroch with antapical end first; two or more prominent circlets of curious spines in second genus. Family ASTYLOZOIDAE Kahl, 1935

Generally stalked, with stalk often noncontractile (but body may be highly contractile); solitary or colonial; great range in sizes [some species of two genera (Campanella, Epistylis) may have zooids up to 600 µm]; abundant in fresh-water habitats (occasionally marine), free or as symphorionts associated with diverse hosts - from other peritrichs to molluscs, crustaceans (barnacle to crab and crayfish: body or gills), aquatic insects, lower vertebrates, etc. - with one genus (Apiosoma) especially widely found on the integument of fresh-water fishes. Family EPISTYLIDIDAE Kahl, 1933

Generally with stalk, noncontractile; solitary or colonial, with highly developed theca in many species; epistomial disc has characteristic appearance of an operculum at anterior end of body; found very commonly as epibionts on fresh-water insects or other arthropods, but one species (Operculariella) is endocommensal in esophagus of a beetle and another (Orsomia) associated with an oligochaete annelid. Family OPERCULARIIDAE Fauré-Fremiet, n. fam.

Stalkless, planktonic, with aboral end of body in advance when swimming; "telotroch" stage permanent (capable of division, etc.); small group of rigid cilia present, separate from (other) oral ciliature and especially distinctive in first genus; cylindrical to bell-shaped body (oral end narrower), with nonstalk-producing scopula at aboral pole and permanent trochal band nearby. Family OPISTHONECTIDAE Foissner, 1976

Solitary, stalkless (yet sessile) forms; adherence to substrata by scopulary organelles forming flattened disc often prominently distinct from rest of body; one group (Ambiphrya) with permanent posterior trochal band; large, gelatinous pseudocolony formed by one free-living planktonic species (Gonzeella); generally found as epibionts on (gills of) fresh-water or marine fishes, molluscs, or other invertebrates (e.g., leeches, marine worms, etc.). Family SCYPHIDIIDAE Kahl, 1933

Body bottle-, vase-, or spindle-shapéd, often with long and highly contractile neck, elongate macronucleus, and aborally located contractile vacuole; solitary (first genus) or forming often huge (up to 15 cm in diameter) gelatinous "spherical" colonies (green-colored from endosymbiotic zoochlorellae in the individual zooids); arypical stalk, sometimes of long peduncular fibers; bonafide species perhaps exclusively fresh-water forms. Family OPHRYDIIDAE Ehrenberg, 1838

Solitary, stalkless forms; fission anisotomic; members of type-genus are particularly distinguished by the remarkable production, on either side of the scopula, of elongate cylindrical projections which encircle a gill filament of their host and glue themselves together to form a closed circle in firm attachment; Ellobiophrya found only as commensal of a marine lamellibranch mollusc, while species of other two genera are associated with marine fishes. Family ELLOBIOPHRYIDAE Chatton & Lwoff, 1929

Scopula produces unique pad-like disc as organelle of attachment~ body is of an inverted cone-shape, with reduced area of oral ciliature and long, helical infundibulum; endocommensals (in the intestine) of certain African termites. Family TERMITOPHRYIDAE Lom, n. fam.

Colonial but with its few zooids in a "group-lorica," a curious structure opened widely at its upper end; the shared stalk is in two sections, one rigid, other highly contractile; found on a marine crustacean (a beach isopod). Family ROVINJELLIDAE Matthes, 1972

Loricate, solitary, with or without a stalk (generally very short when present); oral region of body protrusible well beyond opening of lorica; division isotomic or anisotomic; some species with a true operculum (e.g., Pyxicola); macronucleus usually ribbon-like in form; found attached to plants or inanimate substrata or as symphorionts in both fresh-water and marine habitats. Family VAGINICOLIDAE de Fromentel, 1874

Loricate, solitary, stalkless; relationship of organism's body to lorica unique: attachment is only at opening (loricastome), where complex elastic and contractile lips, collar, etc. are presenn lorica in shape of flattened hemisphere, with surface "glued" to substratum (host's integument) called ventral and the oral end considered anterior; properties of lorica, macronucleus, and (controversially) host-specificity used to distinguish species; most common hosts (with gills as usual site of attachment) are fresh-water amphipods and decapods (especially the crayfish), but salt- and brackish-water shrimps and crabs have also been implicated. Family LAGENOPHRYIDAE Bütschli, 1889

With contractile stalk; all species colonial except in two genera (Haplocaulus, Vorticella); zooids not independently contractile among colonial forms (except in Carchesium); species all attached - to inanimate objects, plants, rotifers, crustaceans (amphipods, decapods, etc.), even turtles, etc. - in various fresh-water and marine habitats.	*Family VORTICELLIDAE* Ehrenberg, 1838**
Stalkless, mobile, planktonic forms, with one or two rigid caudal bristles; organisms resemble zooids of Vorticella broken away from stalk; mature form swims with apical pole forward, telotroch with antapical end first; two or more prominent circlets of curious spines in second genus.	*Family ASTYLOZOIDAE* Kahl, 1935**
Generally stalked, with stalk often noncontractile (but body may be highly contractile); solitary or colonial; great range in sizes [some species of two genera (Campanella, Epistylis) may have zooids up to 600 µm]; abundant in fresh-water habitats (occasionally marine), free or as symphorionts associated with diverse hosts - from other peritrichs to molluscs, crustaceans (barnacle to crab and crayfish: body or gills), aquatic insects, lower vertebrates, etc. - with one genus (Apiosoma) especially widely found on the integument of fresh-water fishes.	*Family EPISTYLIDIDAE* Kahl, 1933**
Generally with stalk, noncontractile; solitary or colonial, with highly developed theca in many species; epistomial disc has characteristic appearance of an operculum at anterior end of body; found very commonly as epibionts on fresh-water insects or other arthropods, but one species (Operculariella) is endocommensal in esophagus of a beetle and another (Orsomia) associated with an oligochaete annelid.	*Family OPERCULARIIDAE* Fauré-Fremiet, n. fam.**
Stalkless, planktonic, with aboral end of body in advance when swimming; "telotroch" stage permanent (capable of division, etc.); small group of rigid cilia present, separate from (other) oral ciliature and especially distinctive in first genus; cylindrical to bell-shaped body (oral end narrower), with nonstalk-producing scopula at aboral pole and permanent trochal band nearby.	*Family OPISTHONECTIDAE* Foissner, 1976**
Solitary, stalkless (yet sessile) forms; adherence to substrata by scopulary organelles forming flattened disc often prominently distinct from rest of body; one group (Ambiphrya) with permanent posterior trochal band; large, gelatinous pseudocolony formed by one free-living planktonic species (Gonzeella); generally found as epibionts on (gills of) fresh-water or marine fishes, molluscs, or other invertebrates (e.g., leeches, marine worms, etc.).	*Family SCYPHIDIIDAE* Kahl, 1933**
Body bottle-, vase-, or spindle-shapéd, often with long and highly contractile neck, elongate macronucleus, and aborally located contractile vacuole; solitary (first genus) or forming often huge (up to 15 cm in diameter) gelatinous "spherical" colonies (green-colored from endosymbiotic zoochlorellae in the individual zooids); arypical stalk, sometimes of long peduncular fibers; bonafide species perhaps exclusively fresh-water forms.	*Family OPHRYDIIDAE* Ehrenberg, 1838**
Solitary, stalkless forms; fission anisotomic; members of type-genus are particularly distinguished by the remarkable production, on either side of the scopula, of elongate cylindrical projections which encircle a gill filament of their host and glue themselves together to form a closed circle in firm attachment; Ellobiophrya found only as commensal of a marine lamellibranch mollusc, while species of other two genera are associated with marine fishes.	*Family ELLOBIOPHRYIDAE* Chatton & Lwoff, 1929**
Scopula produces unique pad-like disc as organelle of attachment~ body is of an inverted cone-shape, with reduced area of oral ciliature and long, helical infundibulum; endocommensals (in the intestine) of certain African termites.	*Family TERMITOPHRYIDAE* Lom, n. fam.**
Colonial but with its few zooids in a "group-lorica," a curious structure opened widely at its upper end; the shared stalk is in two sections, one rigid, other highly contractile; found on a marine crustacean (a beach isopod).	*Family ROVINJELLIDAE* Matthes, 1972**
Loricate, solitary, with or without a stalk (generally very short when present); oral region of body protrusible well beyond opening of lorica; division isotomic or anisotomic; some species with a true operculum (e.g., Pyxicola); macronucleus usually ribbon-like in form; found attached to plants or inanimate substrata or as symphorionts in both fresh-water and marine habitats.	*Family VAGINICOLIDAE* de Fromentel, 1874**
Loricate, solitary, stalkless; relationship of organism's body to lorica unique: attachment is only at opening (loricastome), where complex elastic and contractile lips, collar, etc. are presenn lorica in shape of flattened hemisphere, with surface "glued" to substratum (host's integument) called ventral and the oral end considered anterior; properties of lorica, macronucleus, and (controversially) host-specificity used to distinguish species; most common hosts (with gills as usual site of attachment) are fresh-water amphipods and decapods (especially the crayfish), but salt- and brackish-water shrimps and crabs have also been implicated.	*Family LAGENOPHRYIDAE* Bütschli, 1889**