Dysteria crassipes Claparède & Lachmann, 1859

(Fig. 5 F–I; Table 2)

Morphological description. Cell size about 50 – 60 × 35 – 45 μm in vivo. Body shape oval in side view, with anterior end rounded and posterior end slightly narrowed (Fig. 5F). Two nematodesmal rods, each about 25 μm long. Two contractile vacuoles, about 5 μm across, ventrally positioned at about anterior and posterior third of cell, respec- tively; each pulses at an interval of 1–2 min (Fig. 5F). Dorsal spine absent. Many bar-shaped ectosymbiotic bacteria often detected on cell surface (Fig. 5G). Macronucleus about 25 × 15 μm in vivo. Micronucleus not detected. Mainly feeds on diatoms and bacteria.

Invariably four right kineties with loosely arranged basal bodies including two frontoventral kineties with 89–121 basal bodies each. Six to eight left kineties (Fig. 5H). Two circumoral kineties, one preoral kinety, and three left frontal kineties located in oral area (Fig. 5I). Terminal fragment composed of six or seven kinetosomes (Fig. 5I). Equatorial fragment consists of 4–20 basal bodies.

SSU rRNA gene sequence and phylogenetic position. The GenBank accession number, length, and G + C content, are MK 882889, 1,571 bp, and 45.39%, respectively. The closest related Dysteria form is Dysteria crassipes (KC 753492) with a 99.7% sequence similarity. The sequence similarity of Dysteria crassipes (MK 882889) to D. crassipes (FJ 868206) is 99.5%. Phylogenetic trees (Fig. 6) show our isolate forms a clade with three other forms of C. crassipes with solid support values.