Belbolla sinica Wang & Guo & Wang 2022, sp. nov

Belbolla sinica sp. nov. (Figures 3–4, Table 2) Type material. One male and three females were measured and studied. Holotype: ♂ 1 on slide 19YMD2-4-82; paratypes: ♀ 1, ♀ 2 and ♀ 3 on slides 19YMD2-2-49. Type locality and habitat. Specimens were collected from intertidal muddy sediment (0-2 cm) at Yangma Island, Shandong Province. 37º45′N, 121º61′E. Etymology. The species name means Chinese, the type locality. Measurements. All measurement data are given in Table 2. Description. Males. Body comparatively short, 1405 μm in length, anterior and posterior body end tapered. Cuticle smooth. The anterior body end markedly tapered and body width at level of posterior pharynx end 3.8 times as wide as labial region. Buccal cavity separated into two chambers by a cuticularized ring without denticles, with one large right ventral sublateral tooth, one small left sublateral tooth and one small dorsal tooth. Buccal cavity deep and cuticularized, 9 μm in length (1 head diameter long). Inner labial sensilla papillae, outer labial setae and cephalic setae arranged in one circle, 7 μm in length. Ten cervical setae 34 μm from anterior end, 7 μm in length. Amphidial fovea not observed and ocelli absent. Pharyngeal region well developed, 361 μm in length, posterior region modified into seven bulbs (116 μm in length). Nerve ring situated 203 μm from anterior end. Cardia short, conoid. Testes paired, opposed and outstretched, both located on the left of the intestine. Spicules paired and straight, 36 μm in length (1.3 cloacal body diameter), tapered in proximal and distal end, thickened in the middle part. Gubernaculum short and without apophysis, 9 μm in length. Two winged precloacal supplements small and well developed, anterior precloacal supplement (beginning from center of supplements) 193 μm and posterior 134 μm from cloacal opening respectively. Tail conico-cylindrical in shape, 101 μm (3.6 anal body diameter) in length, and cylindrical part short (16% of tail length). Three caudal glands present in line. Tail with three terminal setae. Females. Similar to males in most characters. Reproductive system didelphic-amphidelphic, with reflexed ovaries, 630–752 μm in length (38% of total body length). Anterior and posterior ovaries on the right of the intestine. Vulva located slightly posterior to the mid-body, 938–1064 μm (55%–56% from anterior end). Vagina short and sclerotized. Differential diagnosis and discussion. Belbolla sinica sp. nov. is characterized by comparatively short body length, posterior pharynx with seven bulbs, spicules straight with proximal and distal end tapered and middle part thickened, gubernaculum short without apophysis, two winged precloacal supplements small and well developed, tail conico-cylindrical with cylindrical portion short. By now, four species of Belbolla, B. asupplementata Juario, 1974; B. gracilis Gagarin & Thanh, 2016; B. heptabulba Timm, 1961 and B. warwicki present 7 pharyngeal bulbs. Belbolla sinica sp. nov. differs from B. asupplementata in the gubernaculum shape (without apophysis vs. with small apophysis), presence of precloacal supplements (two winged precloacal supplements vs. absence of precloacal supplements), and tail length (101–124 μm vs. 146–167 µm). The new species differs from B. gracilis in the spicules length and shape (36 μm, straight vs. 50 μm, slightly arched), gubernaculum shape (without apophysis vs. with long caudal apophysis), precloacal supplements shape (two winged precloacal supplements vs. two round shaped supplements) and tail shape (cylindrical portion short, 13%–16% of tail length vs. cylindrical portion short long, 81% of tail length). The new species differs from B. heptabulba in the spicules shape (straight, proximal end tapered vs. arcuate, proximal end cephalated), presence of gubernaculum (absent in B. heptabulba). The new species differs from B. warwicki in the gubernaculum shape (without apophysis vs. with small apophysis), precloacal supplements shape (two winged precloacal supplements vs. two pocket-shaped precloacal supplements).