Paracoeloperix composita, Wang & Jiang & Pan & Warren & Hu, 2025

Paracoeloperix composita gen. nov., sp. nov.

( Figs 2, 3; Table 1)

ZooBank registration number of new species: urn:lsid:zoobank.org:act:

Diagnosis: Cell size 55–85 μm × 35–50 μm in vivo; body oval, with a spine in posterior left end; CSB closed; finger-like tentacles on ventral side; constantly four anterior and 18–24 posterior somatic kineties; 17–21 nematodesmal rods; one long left and four short anterior terminal fragments; two contractile vacuoles diagonally located; marine habitat.

Type locality: Taipingjiao sandy beach, Qingdao, China ( 36°03′00″N, 120°21′34″E) GoogleMaps .

Type deposition: One protargol slide (registration number: WCC2022102801-1), with the holotype specimen circled in black ink, was deposited in the Marine Biological Museum, Chinese Academy of Sciences , Qingdao. Another protargol slide (registration number: WCC2022102801-2) with paratype specimens was deposited in the Laboratory of Systematic Taxonomy, Ocean University of China, China .

Etymology: Te species-group name ‘ composita ’ is derived from the Latin adjective ‘compositus’, which alludes to its similarity to species of related genera (e.g. Coeloperix, Paralynchella ).

Morphological description: Cell size 70–80 µm × 40–50 µm in vivo ( N = 4), 55–85 µm × 35–50 µm afer protargol staining ( Table 1). Ratio of length to width ~1.7:1. Body outline oval to wide elliptical in ventral view, with a spine (4.5 μm long) in posterior lef end; right margin convex, lef margin straight or concave in starved cells ( Figs 2A, G, 3A, B, F). Ventral side flatened; dorsal side slightly vaulted. A closed CSB positioned at perimeter between ventral and dorsal surfaces, ~4 μm wide, composed of numerous C-shaped clasps ( Figs 2A, F, G, 3C, D). Constantly four finger-like tentacles on ventral side, 8–15 μm long; one tentacle located ~60% down body length, others at lef posterior quarter ( Figs 2G, 3F, H).

Cytoplasmcolourlessandhyaline,containingnumerousirregular grey granules (~2 μm across) ( Fig. 3D) and several food vacuoles (~20 μm across) ( Fig. 3C, E). Cytostome ~10 µm wide, ventrally located at anterior 20% of body length, towards anterior end of cell, supported by 17–21 toothed nematodesmal rods ( Figs 2A, G, 3B, E); cytopharynx ~25 μm long ( Figs 2C, 3K). Macronucleus ellipsoidal, centrally located, heteromerous, ~11 µm × 9 μm in vivo and ~10 µm × 9 μm afer protargol staining ( Figs 2E, G, 3C, G, K). Micronucleus not detected in either live or stained specimens. Two contractile vacuoles, 7 μm in diameter, diagonally positioned ( Figs 2A, 3B). Locomotion by slowly crawling on substrate or by swimming while rotating about ventral longitudinal axis.

Cilia 8–10 µm long in vivo, mainly arranged densely on ventral side ( Figs 2B, 3I). Somatic kineties composed of monokinetids. Anterior and posterior somatic kineties completely separated by cytostome and oral apparatus ( Figs 2B, D, 3I). Constantly four anterior somatic kineties, arched along anterior margin of cell ( Figs 2D, 3I); 18–24 posterior somatic kineties, curved slightly to lef, some basal bodies in middle part sparsely grouped; lef and right fields making an inconspicuous suture ( Figs 2B, 3I). One terminal fragment located at anterior lef margin of cell, with 2–11 basal bodies; four fragments anterodorsally positioned, composed of two to five basal bodies each ( Figs 2E, 3J, K).

Oral ciliature consisting of three perioral kineties parallel to each other, all composed of dikinetids and transversely positioned ( Figs 2D, 3I), anterior one longer with densely arranged kinetids on lef front and sparsely arranged kinetids on right rear; two posterior perioral kineties conspicuously shortened.

Genus Chlamydonella Deroup in Petz et al., 1995