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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Cyrtohymena

Cyrtohymena Foissner, 1989

Family Oxytrichidae Ehrenberg, 1838: Subfamily Oxytrichinae Jankowski, 1979 (ref. ID; 4894)

See Notohymena

[ref. ID; 4894]
Improved characterization; Adoral zone of membranelles formed like a question mark. Undulating membranes in Cyrtohymena pattern. Frontoventral cirri form V-shaped pattern. Postoral ventral cirri in dense cluster underneath buccal vertex. Two pretransverse and five (rarely four) transverse cirri. One right and one left row of marginal cirri. Usually six dorsal kineties. Caudal cirri present. Primordia V and VI of proter originate de novo. Dorsal morphogenesis in Oxytricha pattern. (ref. ID; 4894)
Remarks; This genus is well defined and easily identified by the wide, deep and thus very transparent buccal cavity. However, some species (e.g., C. quadrinucleata, C. tetracirrata, C. primicirrata) deviate from the majority in that the body is rather inflexible, the relative length of the adoral zone is 40-50% of by length, and postoral ventral cirrus V/3 is distinctly displaced posteriad, indicating that it is not involved in primordia formation. Thus, Cyrtohymena is very likely not monophyletic. By non-specialists in vivo easily confused with Steinia which has, however, a very rigid body and a peculiar pit in the buccal cavity. (ref. ID; 4894)
Type species (original designation); Oxytricha (Steinia) muscorum Kahl, 1932 (ref. ID; 4894)
  1. Cyrtohymena australis Foissner, 1995 (ref. ID; 4861 original paper)
  2. Cyrtohymena candens (Kahl, 1932) (ref. ID; 2128) or (Kahl, 1932) Foissner, 1987 (ref. ID; 4861)
  3. Cyrtohymena citrina Berger & Foissner, 1987 (ref. ID; 4861) reported author and year? (ref. ID; 4471)
  4. Cyrtohymena muscorum (Kahl, 1932) Foissner, 1989 (ref. ID; 4795, 7423) reported author and year? (ref. ID; 191)
    Basionym; Steinia muscorum (ref. ID; 7423)
  5. Cyrtohymena primicirrata Berger & Foissner, 1987 (ref. ID; 4861)
  6. Cyrtohymena quadrinucleata (Dragesco & Njine, 1971) (ref. ID; 2128)

Cyrtohymena australis Foissner, 1995 (ref. ID; 4861 original paper)

Diagnosis

Size in vivo 250-400x60-100 um. Cortical granules citrine, 0.4-1 um in diameter, mainly around cirral bases and dorsal bristles. On average 57 adoral membranelles, 37 right marginal cirri, 39 left marginal cirri, and 8 dorsal kineties. Transverse cirri displaced considerably anteriorly. (ref. ID; 4861)

Descriptions

Lanceolate, right margin usually slightly concave, left more or less convex, widest in buccal area, gradually narrowed and broadly rounded at both ends. Very flexible and dorsoventrally flattened up to 2:1. Macronuclear nodules distinctly ellipsoid, in vivo about 45x20 um, in middle third of cell left of median, with many tiny nucleoli. Micronuclei almost spherical, often distant from macronucleus nodules. Contractile vacuole slightly above mid-body at left margin, with two long collecting canals extending anteriorly and posteriorly. Cells yellow at low magnification due to brilliant citrine colour of cortical granules arranged mainly around cirral bases and dorsal bristles, but also in loose rows between cirri and bristles; granules do not impregnate with protargol. Cytoplasm colourless, with some fat globules 2-4 um in diameter and many small and large food vacuoles containing fungal spores, testate amoebae (Trinema lineare, Euglypha spp.), ciliates (Leptopharynx costatus, Drepanomonas pauciciliata), and cysts of Polytoma sp. Moves rapidly to and fro. Marginal and anterior frontal cirri 20-25 um, transverse cirri 30 um long. Marginal rows open at posterior end, gap occupied by caudal cirri right of cell median. Marginal, transverse and caudal cirri form conspicuous fringe at posterior end. Ventral cirral pattern as in other members of genus, but unusually variable, especially in population from Costa Rica. Dorsal cilia about 5 um long, arrange in 5-7 rows almost as long as body and few shortened rows at margins of anterior body half. Bristle complexes composed of 2-6 basal bodies, only one or two of which are, however, ciliated. Oral apparatus and adoral zone of membranelles very conspicuous, occupy about 34% of body length, bases of largest membranelles about 20 um wide. Buccal cavity large and deep. Paroral membrane almost semicircular with two fan-like bundles of fibres at anterior end, in large specimens composed of oblique rows having 4-6 cilia each in anterior and dikinetids in posterior half. Endoral membrane hook-like, extends diagonally across buccal cavity and crosses (optically) paroral membrane in posterior third, very likely composed of dikinetids. Pharyngeal fibres inconspicuous. An early divider (Costa Rica population) showed that morphogenesis commences with the proliferation of basal bodies at the postoral ventral cirri and the uppermost two transverse cirri. (ref. ID; 4861)

Comparison with related species

This large, beautiful species resembles C. citrina Berger & Foissner, 1987 and C. primicirrata Berger & Foissner, 1987 as concerns the yellow cortical granules, body shape and general plane of the somatic and oral infraciliature. However, it is much larger than these species and has thus many more adoral membranelles and right and left marginal cirri. However, the C. australis population from Costa Rica is considerably smaller than that from the type location, indicating a close relationship with the above mentioned Laurasian species. These three yellowly granulated species obviously form a special complex within the genus. (ref. ID; 4861)

Etymology

"australis" refers to the occurrence in the southern hemisphere. (ref. ID; 4861)

Type location

Amazonian rain forest near the town of Iquitos, Peru, W74 degrees, S4 degrees. (ref. ID; 4861)

Type specimens deposited

Slides with type and voucher specimens have been deposited in the Oberosterreichische Landesmuseum in Linz (LI), Austria. Relevant specimens are marked by a black ink circle on the cover glass. (ref. ID; 4861)

Cyrtohymena muscorum (Kahl, 1932) Foissner, 1989 (ref. ID; 4795, 7423) reported author and year? (ref. ID; 191)

Basionym

Steinia muscorum (ref. ID; 7423)

Remarks

Cyrtohymena muscorum and Notohymena rubescens Blatterer & Foissner, 1988 develop nearly the same morphology and the same morphogenetic pattern; both species are separated by a different shape of the undulating membranes. (ref. ID; 7423)