Cinetochilum ovale Gong & Song 2008, n. sp.

Cinetochilum ovale n. sp.

(Figs. 1–21; Table 1)

Diagnosis: Small Cinetochilum about 20–30 × 15–25 µm in vivo. Body oval, with 12–13 bipolar somatic kineties. Scutica comprising two short rows of kinetosomes, positioned near the end of somatic kinety 1. The anterior-most row distinctly detached from the remaining two rows in membranelle 1. Three postoral kinetofragments. One globular macronucleus and one micronucleus. Single contractile vacuole terminally located. A cyrtos-like structure always presents at deep portion of buccal cavity. Marine habitat.

Type location: Intertidal sediment of Tianjin, Bohai Sea, northern China (39°10’N; 117°10’E).

Slide deposition: Protargol impregnated holotype slides of Cinetochilum ovale n. sp. (registration No. 2008:10:9:1) has been deposited in the Natural History Museum, London; one paratype slide (No. G 03071401) has been deposited in the Laboratory of Protozoology, SCNU.

Etymology: The species name “ ovale ”, means oval, referring to the body shape of the organism.

Description: Size in vivo mostly about 25 × 20 µm. Body oval in outline, dorsoventraly flattened about 2:3 (Figs. 1–3, 8–12). Pellicle rigid, ridges between somatic ciliary rows conspicuous, forming a longitudinal suture in apical area (Fig. 5). Buccal cavity elliptic, about 1/3 of body length, positioned in mid-body or slightly posterior to equator, slightly right to median (Figs. 1–3). Endoplasm transparent, with numerous small droplets and tiny crystals (1–1.5 µm across). Single contractile vacuole, 2 µm in diameter, terminally positioned (Figs. 1, 2, 9, 10). Cilia generally equal in length (ca. 5 µm) in vivo, no distinctly long caudal cilium observed though some caudal ones might be slightly longer (Fig. 8, arrowhead).

Oral apparatus generally of Tetrahymena -pattern. Bases of three membranelles (M1–3) obliquely or transversely arranged, usually each composed of three rows of kinetosomes (Figs. 4, 5). The anterior-most row in M1 (double-arrowheads in Fig. 4; arrowhead in Fig. 18) conspicuously shortened, composed of 4 to 5 loosely spaced kinetosomes, and clearly detached from the posterior two rows, which each contains about 12 kinetosomes. M2 and M3 relatively shorter than posterior two rows of M1. Paroral membrane (PM) C-shaped, anteriorly terminating at level of M2, consisting of 25 dikinetids (Figs. 4, 17). One argentophilic cyrtos-like structure (Cy) always present at deep portion of buccal cavity, with approximate 6 short rods (Fig. 4; arrow in Fig. 20). M1–3 all appear 3-rowed as seen at a stage of morphogenesis (Figs. 7, 21).

CV, coefficient of variation in %; Max, maximum; Mean, arithmetic mean; Min, minimum; n, number of individuals examined; SD, standard deviation; SE, standard error of mean.

Somatic kineties (SKs) in 12–13 bipolar rows (Figs. 5, 6, 13–16; Table 1). SKs basically composed of monokinetids, except the SK1 (the first row right to PM), SKn (the last/left row boarding the buccal field) and SKn-1 (the last second row) partially contain kinetosomal pairs, especially in their anterior portions (Figs. 4, 14, 18). SK1 slightly longer than PM, usually all composed of dikinetids. SK2 relatively long, with densely arranged kinetosomes in its anterior portion. SKn and SKn-1 anteriorly terminated near the posterior end of M1 and near the anterior end of SK1, with ca. 7 and 12 dikinetids, respectively. One pair of kinetosomes (arrow) always displaced side by side with the first kinetids of SKn-1 (Fig. 4). Scutica (Sc) comprising two short monokinetid rows, which are close and parallel to the posterior portion of SK1. Postoral kinetofragments (PF) in three short rows, each with about 3 to 5 monokinetids, longitudinally arranged (Fig. 4; arrow in Fig. 19). Macronucleus (Ma) ovoid, diameter about 6 µm after impregnation. One micronucleus (Mi), 2 µm across.