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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Homalozoon

Homalozoon Stokes, 1890 (ref. ID; 2013)

Ciliophora: Rhabdophora (ref. ID; 7284)
Class Kinetofragminophora: Subclass Gymnostomata: Order Haptorida: Family Spathidiidae (ref. ID; 2013)

[ref. ID; 2013]
Body shape elongate (150-1,500 um long), worm-like, flattened laterally, contractile. Posterior with tail-like region of bluntly rounded. Anterior end blunt, slanting slightly posterior from right to left. Oral aperture a slit along the apical edge which consists of a well-defined thickened ridge. Oral region supported by trichites, ridge unciliated but cilia are situated just behind it. The left (upper) surface has three kineties but is devoid of cilia, in some species there is a distinctive longitudinal ridge along its mid-line. The right (lower) surface is ciliated with several (up to about 20) longitudinal kineties. Trichocysts distributed throughout body. Macronucleus usually moniliform, usually along ventral edge. Several contractile vacuoles in line along dorsal edge.
Quote; Colin R. Curds "British and other freshwater ciliated protozoa Part I Ciliophora: Kinetofragminophora" Cambridge University Press, 1982 (ref. ID; 2013)
  1. Homalozoon caudatum Kahl, 1935 (ref. ID; 3690) reported author and year? (ref. ID; 1620)
  2. Homalozoon flexile Stokes, 1890 (ref. ID; 1619, 3540)
  3. Homalozoon vermiculare Stokes, 1887 (ref. ID; 912, 1219, 1619, 1629, 3115, 3540, 7556, 7696) reported year? (ref. ID; 1618) or (Stokes, 1887) Stokes, 1890 (ref. ID; 4612) reported author and year? (ref. ID; 191, 4399, 4686, 7284)
    Syn; Craspedonotus vermicularis (Stokes) Kahl, 1926 (ref. ID; 1619, 3115, 3540, 4612); Leptodesmus tenellus Zacharias, 1888 (ref. ID; 3115, 3540) reported year? (ref. ID; 1619); Litonotus vermicularis Stokes, 1887 (ref. ID; 4612)

Homalozoon vermiculare Stokes, 1887 (ref. ID; 912, 1219, 1619, 1629, 3115, 3540, 7556, 7696) reported year? (ref. ID; 1618) or (Stokes, 1887) Stokes, 1890 (ref. ID; 4612) reported author and year? (ref. ID; 191, 4399, 4686, 7284)

Synonym

Craspedonotus vermicularis (Stokes) Kahl, 1926 (ref. ID; 1619, 3115, 3540); Leptodesmus tenellus Zacharias, 1888 (ref. ID; 3115, 3540) reported year? (ref. ID; 1619); Litonotus vermicularis Stokes, 1887 (ref. ID; 4612)

Descriptions

Standing fresh water. (ref. ID; 1618)
Homalozoon vermiculare is a large, bottom-dwelling, carnivorous ciliate. The nuclear apparatus of H. vermiculare consists of about 25 micronuclei and a single moniliform macronucleus, which is subdivided into an average of 23 segments. The number of segments roughly correlates with cell size. Individual segments can be clearly identified by light microscopy, whereas the connecting intersegments are not visible after Feulgen-staining. If food it abundant, the number of segments, as well as cell length, increases during interphase. At first, the segment grows in length while its width remains unchanged. If the segment length exceeds 20 um, a small zone containing relatively little chromatin frequently can be detected in the center of the segment. Later, the segment constricts in the middle and both halves connect by a narrow isthmus. Eventually, two segments are formed. Just after separation, the segments are still connected by a chromatin-containing stalk. Cell division is preceded by fusion of the segments of the macronucleus. Segment width remains approximately 6-10 um, but segment length increases to three to five times the diameter. Each segment has the ability to fuse with a neighboring segment. Thus, the long segments that are the product of the fusion of individual segments can be observed of the along the complete length of the cell. Although most of the longer segments have been observed in the middle of the cell, the longest segments may just as well appear close to the two ends of the macronuclear chain. In any case, fusion of the segments does not initiated from a single segment running orad or caudad as was described for Homalozoon and other ciliates. When all segments are fused, the macronucleus starts to contract. At the same time, some micronuclei are in anaphase or telophase while other do not divide at all. Eventually the macronucleus forms a single ovoid body. In very few cases Homalozoon has more than one macronucleus. Here, the macronuclei do not fuse but contract independently. After maximal contraction, the macronucleus elongates again. At the time when the division furrow appears, renodulation has started. Several minutes before cell division actually takes place, the macronuclei of the two future daughter cells are connected by a thin Feulgen-positive strand. (ref. ID; 4399)
The nuclear apparatus. (ref. ID; 7284)

Measurements

Body 150-1500 um long. (ref. ID; 1618)