Ophrydium Bory, 1826 (ref. ID; 2014)
Class Oligohymenophora: Subclass Peritricha: Order Peritrichida: Suborder Sessilina (ref. ID; 2014)
Family Ophrydiidae Kent (ref. ID; 1248)

Synonym; Gerda Claparede & Lachmann (ref. ID; 1618)

[ref. ID; 2014]
Colonial. Elongate tubular body, often narrowed posteriorly, lying within a common, very large gelatinous matrix which may be several centimeters in diameter. Complete colony shape highly variable but approximately spherical and sometimes flattened with an overall green tinge due to zoochlorellae in the zooids. The peristomial disc is raised above the peristomial rim. Macronucleus elongate and ribbon-like. Most easily confused with Gerda which is solitary and with Gonzeella in which the colonies are hollow and round with the zooids embedded only in the outer layer of the gelatinous housing.
Quote; Colin R. Curds, Michael A. Gates and David McL. Roberts "British and other freshwater ciliated protozoa Part II Ciliophora: Oligohymenophora and Polyhymenophora" Cambridge University Press, 1983 (ref. ID; 2014)

Ophrydium ectatum Mast (ref. ID; 1618)
Description; With many zoochlorellae; in fresh water. (ref. ID; 1618)
Measurements; 225-400 um long; colony up to 3 mm. in diameter. (ref. ID; 1618)
Ophrydium naumanni Pejler (ref. ID; 2554 original paper, 4613)
Description; On a few occasions Pejler encountered the form which Naumann (1925) designates as a "planktic modification of Ophrydium versatile Ehrenberg". However, several facts indicate that this form, here called O. naumanni, constitutes a separate species: (1) While O. versatile s. str. is not only a littoral but mostly also a sessile form. O. naumanni is a decided plankter, found in net samples with no traces of bottom material. (2) O. naumanni is considerably smaller than O. versatile s. str. The individuals in Pejler samples from Central Sweden measured only about 50 um in length, while such of O. versatile s. str. can attain a length of 400-500 um and even more (Penard 1922). (3) The number of individuals observed in a colony was in O. naumanni mostly only one or two, more rarely three to five, on one occasion up to twenty. On the other hand the colonies of O. versatile s. str. contain thousands of individuals, the diameter of a colony being up to several centimeters. (4) O. versatile s. str. is a eurytopic form, being found in eutrophic as well as in oligotrophic lakes, and in addition in ponds, pools and running water. Pejler have also found it in decidedly brackish water off the coast of Uppland. In contrast O. naumanni has been encountered only in oligtrophic lakes. Of course the possibility cannot be entirely excluded that O. naumanni is in reality a juvenile form of O. versatile. However, as long as no intermediate forms are met with, Pejler justified in considering it a species of its own. Like O. versatile, O. naumanni is stuffed with zoochlorellae. (ref. ID; 2554)
Ophrydium sessile Kent, 1881 (ref. ID; 1620, 1629, 2245) or 1882 (ref. ID; 4610) reported year? (ref. ID; 1618, 3343)
Description; Colorless or slightly brownish; attached to freshwater plants. (ref. ID; 1618)
Measurements; Fully extended body up to 300 um long; ovoid colony up to 5 mm. by 3 mm. (ref. ID; 1618)
Length of cells 150 um, diameter of the colony 360 um. (ref. ID; 3343)
Ophrydium vernalis Stokes (ref. ID; 1618)
Description; Highly contractile; in shallow freshwater ponds in early spring. (ref. ID; 1618)
Measurements; About 250 um long. (ref. ID; 1618)
Ophrydium versatile (O.F. Muller, 1786) (ref. ID; 1114, 1219, 1620, 1629, 2245, 2554) reported year? (ref. ID; 3698) or (O.F. Muller, 1786) Ehrenberg, 1830 (ref. ID; 4610, 4613)
Syn; Ophrydium versatile var. acaulis Roux, 1901 (ref. ID; 1620); Vorticella versatilis O.F. Muller, 1786 (ref. ID; 4610, 4613)
Description; Body elongated flask-form, the "neck" is extremely contractile; green in color on account of symbiotic zoochlorellae; long dichotomous stalk; macronucleus long, band-like, extending along the longitudinal axis of the cell; several strains are amicronucleate; contractile vacuole with a long vacuolar canal that empties into the buccal cavity; individuals are embedded in a large mucilaginous mass that is attached to various substrates (e.g., stones, sticks, shell, plants); small colonies are nearly spherical, larger colonies are of an irregular spherical form, sometimes flattened, often with a central cavity; dispersal by telotrochs, which are equipped with an aboral locomotory girdle of cilia. (ref. ID; 1219)
Measurements; Individual 300-600 um long (fully extended), colonies up to 15 cm. (ref. ID; 1219)