Urosomoida Hemberger, 1981 (ref. ID; ?) or 1985 (ref. ID; 4697 original paper), Hemberger in Foissner, 1982 (ref. ID; 4894)
Family Oxytrichidae Ehrenberg, 1838: Subfamily Oxytrichinae Jankowski, 1979 (ref. ID; 4894)

[ref. ID; 4894]
Improved characterization; Adoral zone of membranelles formed like a question mark. Undulating membranes in Oxytricha pattern. Frontoventral cirri in V-shaped pattern. Postoral ventral cirri in dense cluster underneath buccal vertex. One pretransverse ventral cirrus and less than four transverse cirri. One right and one left row of marginal cirri. Four dorsal kineties. Caudal cirri present. Primordia V and VI of the proter originate de novo. Dorsal morphogenesis in Urosomoida pattern. (ref. ID; 4894)
Remarks; Foissner (1982) published the diagnosis proposed by Hemberger (1982) verbatim. Thus, the appropriate citation of the genus is "Hemberger in Foissner 1982" (article 50a of the ICZN 1985). Some species can be confused with Sterkiella spp., which have, however, a broader and less flexible body. Often difficult to separate from Oxytricha. (ref. ID; 4894)
Type species (original designation); Uroleptus agilis Engelmann, 1862 (ref. ID; 4894)


Urosomoida antarctica (ref. ID; 2128 original paper)
Description; Two postoral ventral cirri, 2 caudal cirri, 4 dorsal kineties. On average 20 adoral membranelles, 17 right marginal cirri, 19 left marginal cirri, and 5 transverse cirri. Shape broadly elliptical, posteriad usually slightly widened, both ends broadly rounded. Flexible like, e.g., Oxytricha granulifera and U. granulifera, and dorsoventrally flattened up to 2 : 1. Macronuclear nodules distinctly ellipsoidal, in middle third of cell to left of midline. Micronuclei slightly ellipsoidal, number rather variable, if only 1 is present it is usually attached to the anterior macronuclear nodule. Contractile vacuole in mid-body near left margin, without distinct collecting canals. Cortex colourless, flexible, without special granules. Cytoplasm colourless, contains many 2-3 um sized, colourless fat globules, some small vacuoles with yellowish, crystalline content, and many 4-6 um sized food vacuoles. Feeds on bacteria and, possibly, also on heterotrophic flagellates and small naked amoebae. Moves slowly. All cirri strikingly thin, anterior frontal cirri, transverse cirri and caudal cirri about 18 um, other cirri 12 um long. Marginal rows open widely at posterior end, gap occupied by posteriormost transverse cirri and caudal cirri. Ventral and dorsal infraciliature very similar to that of U. agiliformis, except for the lacking third postoral cirrus and the normal set of transverse cirri. Dorsal cilia 3 um long; kinety 1 shortened anteriorly, kinety 4 terminates pre-equatorially. Oral apparatus and adoral zone of membranelles inconspicuous, occupy about 32% of body length, bases of largest membranelles in vivo about 6 um wide. Buccal cavity narrow and flat. Paroral and endoral membrane almost straight, slightly intersecting optically. Pharyngeal fibres inconspicuous. (ref. ID; 2128)
Note; The generic classification of U. antarctica is uncertain and requires ontogenetic data. The arrangement of the undulating membranes and the full set of transverse cirri indicate that it might belong to Oxytricha, whereas the reduced number of postoral and caudal cirri and three simple dorsal infraciliature resemble Urosomoida. In any case, this species has a unique combination of characters not found in any other known species. (ref. ID; 2128)
Etymology; Name after the continent found. (ref. ID; 2128)
Measurements; In vivo about 60-75 x 25-35 um. (ref. ID; 2128)
Urosomoida granulifera Foissner, 1996 (ref. ID; 2128 original paper)
Description; Cortical granules colourless, about 1 um in diameter, form small, irregularly arranged patches. On average 23 adoral membranelles, 24 right marginal cirri, 23 left marginal cirri, 4 transverse cirri, and 2 caudal cirri. Shape highly variable, slenderly to broadly elliptical or parallel-sided, sometimes slightly fusiform, both ends narrowly to broadly rounded. Flexible like, e.g., U. agiliformis and Oxytricha granulifera, dorsoventrally flattened up to 2 : 1. Usually 2, very rarely 3 distinctly ellipsoidal macronuclear nodules in middle third of cell to left of midline. Micronuclei ellipsoidal, number highly variable, however, most specimens have 2. Contractile vacuole in mid-body at left margin, with 2 inconspicuous collecting canals extending anteriorly and posteriorly. Cortex colourless, flexible, cortical granules inconspicuous because colourless, minute and sparse, form irregular groups composed of up to 30 granules. Cytoplasm colourless, contains many small, yellowish crystals. Possibly feeds on bacteria. Movement moderately rapid, scrabbing amongst soil particles. Anterior frontal cirri, transverse cirri and caudal cirri about 18 um, other cirri 12 um long. Marginal rows open at posterior end, gap occupied by posteriormost transverse cirrus and caudal cirri. Ventral and dorsal infraciliature very similar, if not to say identical to that of U. agiliformis. Dorsal cilia 4 um long in vivo. Oral apparatus and adoral zone of membranelles also very similar to that of U. agiliformis, i.e. inconspicuous, occupy about 34% of body length, bases of largest membranelles in vivo about 7 um wide. Buccal cavity narrow and flat, right half and posterior third of adoral zone covered by hyaline lip. Paroral and endoral membrane almost straight, extend side by side diverging posteriorly. Pharyngeal fibres inconspicuous. (ref. ID; 2128)
Notes; The new species is most similar to U. agiliformis Foissner, 1982 as concerns size, shape and most morphometric and morphologic characteristics of the infraciliature. However, U. agiliformis and other similar oxytrichids discussed by Ganner et al. (1987) lack cortical granules. In this respect, U. granulifera resembles U. agilis whose granules, however, usually have a yellowish to reddish colour. Furthermore, U. agilis has 3 caudal cirri and it posterior portion is always more or less distinctly elongated. Urosomoida minima Hemberger, 1985 has only 14-15 adoral membranelles and an unusual number, viz. 5, of posterior frontal cirri. Urosomoida perthensis Foissner and O'Donoghue, 1990 has 3 caudal cirri and a single micronucleus interposed between the macronuclear nodules. (ref. ID; 2128)
Etymology; granulifera (bearing granules) refers to the main species character, viz. the cortical granules. (ref. ID; 2128)
Measurements; In vivo about 70-100 x 20-30 um. (ref. ID; 2128)