Halichoanolaimus zhangi, Huang & Zhai, 2024

Huang, Mian & Zhai, Hongxiu, 2024, Two new species of the genus Halichoanolaimus (Nematoda, Selachinematidae) from the intertidal zone of the Yellow Sea, China, ZooKeys 1208, pp. 259-274 : 259-274

Halichoanolaimus zhangi sp. nov.

Figs 3 , 4 , 5 , Table 2

Material examined.

Two males and one juvenile were obtained. Holotype: ♂ 1 on slide 22 HSB-11-2-1 ; paratypes: ♂ 2 and juvenile on slide 22 HSB-11-2-2 . Type specimens were deposited in the Marine Biological Museum of the Chinese Academy of Sciences, Qingdao.

Type locality and habitat.

Holotype and paratypes were found from intertidal muddy sediment at Rizhao coast along the Yellow Sea; 35 ° 18 ' N, 119 ° 31 ' E; 0–2 cm sediment depth.

Etymology.

The specific epithet “ zhangi ” is in honor of Professor Zhinan Zhang, a Chinese nematologist, in recognition of his contributions to nematode taxonomy.

Measurements.

All measurement data are given in Table 2 .

Description.

Males. Body cylindrical, tapering slightly towards posterior end. Cuticle with transverse rows of punctations. Lateral differentiation presents except to anterior half of pharynx with even punctations. Lateral differentiation consisting of slightly larger and more widely spaced punctations. Four longitudinal rows of pore complexes situated at sublateral sides of pharyngeal region (Fig. 4 B ). Each row with 10–12 pores. Cephalic region slightly rounded. Inner and outer labial sensilla papillose; four cephalic sensilla setiform, 4–5 µm long. Amphideal fovea multispiral with 3–3.25 turns, located at the level of the buccal cavity base, 27–28 µm from anterior end of body. Buccal cavity large, 43–45 µm deep, divided into anterior and posterior portions by two rows of 25 denticles. Anterior portion of buccal cavity cup-shaped, with three sets of three cuticularized rhabdions, terminating in three sets of paired denticles; posterior portion of buccal cavity narrower, cylindrical, surrounded by three Y-shaped pairs of cuticularized rhabdions with swollen bases, ca 20 µm long. Pharynx cylindrical, muscular, without anterior or posterior bulb; pharyngeal lumen cuticularized. Nerve ring difficult to distinguish. Secretory-excretory system present. Ventral gland small, situated at level of cardia; ampulla large, excretory pore situated at position of three corresponding body diameters from the anterior end. Cardia small, partially surrounded by intestine.

Reproductive system diorchic with two opposed, outstretched testes. Anterior testis to the right or ventrally to intestine, posterior testis to the left side of intestine. Spicules paired, curved, gradually narrowing from proximal to distal end with pointed tip, ca 2 cloacal body diameters long. Gubernaculum rod-like, adjoining to the dorsal side of spicules. 7 papilliform precloacal supplements, the most posterior supplement located 14 µm from the cloaca; remaining supplements gradually increasing the spacing distance forward, from 9 µm to 26 µm to each other. Each supplement consists of conical papilla and an internal duct. Two rows of short conical setae situated at two subventral sides of the precloacal supplements region of body. Tail conical with a long posterior filiform portion, accounts for 92 % total tail length. A row of 5 caudal setae distributed at ventral side of tail conical part, 3–4 µm long. Caudal glands and spinneret present, 7 µm long.

Female not found. Juvenile similar to males in body shape, and with a long filiform tail, except body size smaller, intestine with blind end.

Differential diagnosis and discussion.

Halichoanolaimus zhangi sp. nov. is distinct by lateral differentiation presenting posterior to the middle of the pharynx, amphideal fovea with 3.0–3.3 turns, spicules curved, gradually narrowing from proximal to distal end with pointed tip, 7 papilliform precloacal supplements, gradually increasing the spacing distance forward, two rows of subventral stout setae situated at precloacal region, tail elongated, filiform. The new species is most similar to H. possjetiensis Belogurov & Fadeeva, 1980 in the filiform tail and number of precloacal supplements, but differs from the latter species by body slender (a = 38.6–38.9 vs body stout, a = 25.8–26.6), longer tail (c = 4.9–5.2 vs c = 8–8.3) and different gubernaculum (slender and straight vs. broad and hooked proximally in H. possjetiensis ).

Figures

Figure 3. Drawings of Halichoanolaimus zhangi sp. nov. A pharyngeal region of holotype B anterior end of holotype C cloacal region of holotype D posterior end of male 2. Scale bars: 30 μm (A, B, C); 50 μm (D).

Figure 4. Microscopic images of Halichoanolaimus zhangi sp. nov. A anterior end of holotype, showing buccal cavity and excretory pore (arrow) B anterior end of holotype, showing cephalic seta (arrow 1) amphidial fovea and cuticle pores (arrow 2) C posterior portion of male 2, showing spicules and tail D cloacal region of holotype, showing spicules, gubernaculum and supplements. Scale bars: 20 μm (A, B, D); 50 μm (C).

Figure 5. Microscopic images of Halichoanolaimus zhangi sp. nov. A anterior end of holotype, showing lateral differentiation and somatic setae (arrow) B cloacal region of holotype, showing lateral differentiation and conical setae situated at two subventral sides of precloacal supplements (arrow) C anterior end of juvenile, showing buccal cavity and cephalic sensilla (arrow) D posterior portion of juvenile, showing the end of intestine (arrow). Scale bars: 20 μm (A, B, C, D).