Chlamydodon pararoseus sp. n.

(Figs 2, 3; Table 1)

urn: lsid: zoobank.org: act: CABCE2B6-C7B8-4E64-88F0-4DF76763492F

Diagnosis. Cell 70–100 μm long in vivo, broadly bean-shaped to kidney-shaped in outline; cross-striated band complete; two yellowish brown to reddish pigment spots in anterior-left and posterior-right of cell, respectively; 44–51 somatic kineties including 23–28 right, 16–19 left, and four postoral kineties; 11–14 nematodesmal rods; two to four terminal fragments. Marine habitat.

Zoobank registration of Chlamydodon pararoseus sp. n.: urn: lsid: zoobank.org: act: CABCE2B6-C7B8-4E64- 88F0-4DF76763492F

Type locality. Seawater in a rocky tidal pool in Taiping Bay, Qingdao, northern China (36°03'N, 120°21'E) .

Type slides. A protargol slide including the holotype specimen (Fig. 2E, F) and another slide with paratype specimens are deposited in the Laboratory of Protozoology, OUC, China, with the registration numbers: WCC2018041901-1 & WCC2018041901-2

Etymology. The specific epithet “ pararoseus ” is derived by adding the Greek prefix “para-” (meaning “beside, at, along, during”) to the epithet “ roseus,” in recognition that this species morphologically closely resembles C. roseus .

Morphological description. Size 70–100 × 50–60 µm in vivo, and 65–90 × 30–50 µm after protargol staining. Body broadly bean-shaped or kidney-shaped with both ends evenly rounded (Figs 2A, 3A); right margin slightly convex and left one somewhat concave (Figs 2A, 3D, F); cell dorsoventrally compressed with a width-thickness ratio of about 4:1. Cross-striated band complete, 1–2 μm wide, comprising about 140 C-shaped clasps. Two small yellowish brown to reddish pigment spots positioned in anterior-left and posterior-right of cell, respectively (Figs 2 A–C, 3A–F). Many bright brown granules (about 0.5 μm across) distributed mainly along ciliary rows. Cytoplasm contains many undigested reddish to brown pigments or ingested particles (4–8 µm across; Fig. 3 A–C). Cytostome elliptical, located at approximately anterior 30% of cell, about 16 μm long; cyrtos composed of 11–14 nematodes- mal rods, each about 25 μm long (Figs 2D, 3A, E). About 20–30 contractile vacuoles (2–4 μm across, counted from three live individuals) irregularly distributed (Figs 2A, 3A), with a contraction interval of about 4 seconds. A single ellipsoidal, heteromerous macronucleus, about 25 × 20 μm in vivo and after fluorescent staining, and about 20 µm across after protargol staining, located in mid-body (Figs 2A, F, 3A, G). Micronucleus not detected. Cells crawl on the substrate or swim in water by rotating around the longitudinal axis of cell.

Cilia about 5 μm long in vivo. In total 44–51 somatic kineties including 23–28 right, 16–19 left, and invariably four postoral kineties; somatic kineties densely arranged, mostly confined to region surrounded by cross-striated band. Anterior ends of right kineties extend beyond level of cytostome and bend to left; outermost 10–12 right kineties usually extend onto dorsal surface and the innermost one is interrupted by oral kineties. Left kineties extend sub-apically and form a hook-like suture with right kineties (Figs 2E, G, 3H). A sub-equatorial fossa with four or five kineties on the ventral side (Figs 2E, 3B, L). Two to four terminal fragments, each composed of 4–15 basal bodies, arranged in a row adjacent to the outermost right kinety on dorsal side (Figs 2F, 3K). Equatorial fragment not detected.

Three oral kineties obliquely oriented: two circumoral kineties parallel and closely arranged to each other, the outer row longer than the inner one; preoral kinety located in anterior-left of circumoral kineties (Figs 2E, G, 3I). One circle of barren kinetosomes (corresponding to position of tips of nematodesmal rods) observed surrounding cytostome in protargol-stained specimens (Figs 2G, 3J).

SSU rRNA gene sequence and phylogenetic position. The new SSU rRNA gene sequence has the GenBank accession number, length, and G + C content of MK 882886, 1,582 bp, and 45.64%, respectively. The closest related Chlamydodon species are the Qingdao population of Chlamydodon bourlandi (MK 882887) in present work and C. obliquus (FJ 998030, = C. bourlandi, as shown in Qu et al., 2018a), each with a 95.5% sequence similarity. In phylogenetic trees (Fig. 6), C. pararoseus sp. n. clusters with the clade comprising three Chlamydodon species and Paracyrtophoron tropicum, with medium to full support values (ML /BI, 88%/1.00).