Pseudotetrahymena orientalis Wang & Liu & Wang & Wang & Wang & Wang & Zhao & Pan 2025, gen. et sp. nov.

Pseudotetrahymena orientalis gen. et sp. nov. urn:lsid:zoobank.org:act: AD200533-1E68-4CF5-BE38-1CB4104F26A8 Figs 2–3; Table 1 Diagnosis Size in vivo 165–230 × 125–210 μm; anterior end pointed and posterior end broadly rounded; buccal field big and deep, approximately 40% of body length; 19 or 20 somatic kineties; two postoral kineties; M1 and M2 approximately equal length; M2 consists of three parts (M2a, b, c); M3 obviously shorter than M1 and M2; one macronucleus. Micronucleus not observed; freshwater habitat. Etymology The species-group name ‘ orientalis ’ (Latin adjective; eastern, occurring in the Orient) refer to the fact that this species was discovered in East Asia. Type material Holotype CHINA – Heilongjiang Province • Harbin City, Dafa international fish market [a freshwater aquarium]; 45°44′9″ N, 126°35′41″ E; 11 Oct. 2022; Xiang Wang leg.; HANU WX-20221011-01 (carbonate-stained slide with 6 specs, the holotype specimen marked with an ink circle). Paratypes CHINA – Heilongjiang Province • 5 specs; same collection data as holotype; HANU WX-20221011-02. Type locality A freshwater aquarium at Dafa international fish market in Harbin (45°44′9″ N, 126°35′41″ E), Northeast China. Description Size in vivo 165–230 × 125–210 μm; body shape flexible, anterior end narrowed and posterior end broadly rounded usually (Fig. 2A–B, E, H–I, K). When food vacuoles filled by food, 60% of posterior part of cell swells extremely (Fig. 2A, E). Ratio of length to width about 1.5:1. Buccal field usually big, deep, and oval, approximately 40% of body length (Fig. 2A, E, H–I; Table 1). Cortical granules spherical, arranged randomly on pellicle (Fig. 2H, J–K). Cytoplasm colorless to deep dark when food vacuoles filled with food (Fig. 2A, E, H–I, K), often containing several big food vacuoles filled with ingested Tetrahymena (food vacuoles about 40 μm in diameter) (Figs 2K, 3G). Single contractile vacuole (approximately 25 μm in diameter) positioned close to posterior end (Fig. 2K). Extrusomes not observed; single ellipsoid macronucleus, approximately 60 μm across after staining, usually squeezed by food vacuoles, no micronucleus observed (Fig. 3A–D, H). Length of somatic cilia approximately 10 μm, densely arranged. Locomotion mainly by swimming slowly, sometimes rotating forwards. Preying on Tetrahymena. Altogether 19 or 20 SK arranged latitudinally, extending the entire length of body, consisting of monokinetids (Figs 2C–D, 3A–D). Two PK; PK1 and PK2 commence anteriorly at level posterior of PM and extend posteriorly nearly to end of cell (Figs 2F, 3C). Oral structure consisting of one PM and three oral membranelles (Figs 2C, F–G, 3E–F). PM generally C-shaped, composed of paired basal bodies, organized in zigzagging pattern, extending anteriorly to M2. (Figs 2F–G, 3E–F). M1 and M2 approximately equal in length, composed of four or three rows of kinetids (Figs 2F–G; 3E–F). M2 consisting of three parts, namely M2a, b, c. M2a not obvious anteriorly and conspicuous posteriorly, composed of two rows of kinetids (Figs 2F–G, 3E–F). M2b obvious, consisting of four rows of kinetids (Figs 2F–G, 3E–F). M2c divided into two parts, each composed of four rows of kinetids (Figs 2F–G, 3E). M3 shorter than M1 and M2, containing three rows of kinetids (Fig. 3E–F). Gene sequences The SSU-rRNA gene sequence of Pseudotetrahymena orientalis gen. et sp. nov. ahas been deposited in GenBank database with the accession number OR616813.