Cyclidium paravorax Wang & Liu & Wang & Wang & Wang & Wang & Zhao & Pan 2025, sp. nov.

Cyclidium paravorax sp. nov. urn:lsid:zoobank.org:act: EFC1DA92-72AD-4EA2-936F-12805A06A0EA Figs 4–5; Tables 1–2 Diagnosis The cell about 20–30 × 15–25 µm in vivo; the buccal field occupies about 40–45% of the body length; nine somatic kineties; SKn extends to posterior sub-terminally; one or two macronuclei and one micronucleus; M1 consists of two longitudinal rows and is obviously shorter than M2; M2 has a long-triangle shape; M3 consists of four basal bodies in one row; the scutica is mainly composed of two pairs of kinetosomes; single caudal cilium; freshwater habitat. Etymology The species-group name ʻ paravorax ʼ is a composite of the Greek adjective ʻpara-ʼ (beside) and the species-group name ʻ vorax ʼ, indicating its similarity to Cyclidium vorax Pan, 2020. Type material Holotype CHINA – Heilongjiang Province • Harbin City, Harbin Normal University; 45°52′3″ N, 126°33′2″ E; 23 Nov. 2022; Xiang Wang leg.; HANU WX-20221123-01 (carbonate-stained slide with 22 specs, the holotype specimen marked with an ink circle). Paratypes CHINA – Heilongjiang Province • 39 specs; same collection data as holotype; HANU WX-20221123-02. Type locality A freshwater aquarium at Harbin Normal University, Harbin (45°52′3″ N, 126°33′2″ E), Northeast China. Description Body about 20–30 × 15–25 µm in vivo, ellipsoidal with flat section in anterior end, posterior end slightly wider (Fig. 4A, K–N). Ratio of length to width about 1.25:1. Buccal field about 40%–45% of body length, with prominent paroral membrane on ventral side (Fig. 4A, K–P; Table 1). Cortex smooth. Somatic cilia and cilia of paroral membrane about 6 µm long (Fig. 4K–N), single caudal cilium about 13 µm long (Fig. 4A, K, N, P). Cytoplasm colorless, containing several (approximately 1 µm in diameter) bacteriafilled food vacuoles and variable-sized (0.5–1 µm) granules (Fig. 4A, K, N). Contractile vacuole located near posterior end of cell, approximately 4 µm in diameter (Fig. 4A, K–L, N). Extrusomes not observed; one or two globular macronuclei approximately 7 µm in diameter (eight out of 23 cells examined with two macronuclei); one micronucleus approximately 2 µm across after staining (Figs 4E, 5K–L). Locomotion by swimming fast, sometimes motionless for long periods. Altogether 9 or 10 SK extending from near anterior end to near posterior end (Figs 4B–C, 5A–B), all consisting of dikinetids in its anterior half and widely positioned monokinetids posteriorly (Fig. 5E, K). SKn consisting of 10 to 13 kinetids; SK 1 composed of 14 kinetids. PM generally L-shaped, occupies about 40%–45% of body length, composed of zigzagging structure (Figs 4D, 5C). M1 consists of two longitudinal rows of monokinetids, shorter than M2 (Figs 4D, 5D); M2 long-triangle shaped, composed of three longitudinal rows and 8 horizontal rows (Figs 4D, 5C); M3 obviously smaller and shorter than M1 and M2, bearing one row consisting of four basal bodies (Figs 4D, 5C). Scutica patterns diversified (Figs 4F–J, 5F–J), arranged in two groups mainly (Figs 4D, F, 5F), located near posterior end of PM; each part composed of two and four basal bodies. Gene sequences The SSU-rRNA gene sequence of Cyclidium paravorax sp. nov. has been deposited in GenBank database with the accession number OR466404.