Cobbia zhangi sp. nov.

(Figures 3 and 4)

Type material. Three males and two females were found. Holotype male on slide 3800-5-0-14. Paratypes: two males on slide 3800-5-0-11 and slide 3800-5-0-12 respectively, two females on slide 3800-5-0-10.

Type locality and habitat. Sea floor of the Yellow Sea. Station 3800-5 (38°25′ N, 122°30′ E), water depth 50 m, muddy sediment.

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

Measurements. All measurement data are given in Table 2.

Descriptions.

Males. Slender body with rounded anterior and tapered posterior end. Cuticle striated. Somatic setae sparse, 10–16 µm in length. Lip region high and rounded.Anterior sensilla arranged into two distinct circles. Six inner labial sensilla setiform, 3 µm long. Six outer labial setae and four cephalic setae forming a posterior circle. Outer labial setae longer than cephalic setae and very close to each other. Amphidial fovea circular, 33%–38% corresponding body diameter, located 31–32 µm from anterior end, i.e. 4–4.6 times of the amphidial fovea. Buccal cavity funnelshaped with three teeth; a dorsal tooth and two subventral teeth almost the same size. Pharynx muscular, cylindrical in shape without terminal bulb. Nerve ring located at 53%–57% pharynx length. Secretory-excretory system not observed. Cardia elongated, conical, fully inserted into the intestine. Tail elongated, flagelliform, conically tapering to the anterior quarter, whence follows a thin filiform part, without terminal setae. Caudal glands difficult to see.

Reproductive system diorchic.Anterior testis located to the left side of intestine; posterior testis smaller, located to the right side of intestine, about two-thirds the length of the former. Vas deferens long, ventral to intestine. Spicules equal in size, 1.16–1.2 cloacal body diameter, slightly curved, cephalated proximally and tapered distally. Gubernaculum simple, rod-like, without apophysis.

Females. Similar to males in most morphological characteristics except tail slightly longer. Vulva slit-like, opens at mid-body. Vagina surrounded by glandular cells. Reproductive system monodelphic, with an outstretched anterior ovary located to the left side of intestine. Spermatheca present, just anterior to vulva.

Differential diagnosis and discussion. Cobbia zhangi sp. nov. is characterized by having three similar equal-sized teeth, anterior sensilla arrangement 6+10, slightly curved spicules cephalated proximally and tapered distally, gubernaculum rod-like without apophysis, tail with posterior three fourths filiform part. The new species is similar to C. triodonta Filipjev, 1918 and C. truncata Wieser, 1959 in having three similar equal-sized teeth, but differs from C. triodonta by smaller body size (a = 48.8–54.5 versus a = 56.9–66.7), larger amphidial fovea (33%–38% versus 20% corresponding body diameter) and tail with posterior three fourths filiform part (versus tail with posterior third filiform part in the latter species), the new species differs from C. truncata by anterior sensilla arrangement pattern 6+10 (versus anterior sensilla arrangement 6+12), gubernaculum apophysis absent (versus gubernaculum with a varying apophysis), much larger body (a = 48.8–54.5 versus a = 32.3) and much shorter tail (c = 3.5–4.5 versus c = 7.1). In having 6+10 arrangement pattern of anterior sensilla and filiform tail, this new species resembles C. kamenevi Fadeeva & Malysheva, 1991, but differs by buccal cavity with three teeth almost equal-sized (versus one large dorsal and two small subventral teeth), outer labial setae 15–19 µm long, 1–1.3 times as head diameter (versus 9–12.5 µm long, as 0.6–0.8 times head diameter), spicules arcuated, 24–29 µm long, as 1.1–1.2 times a.b.d. (versus 44.1–54.1 µm long, as 1.3–1.5 a.b.d.) and gubernaculum tubular with three teeth at distal end in the latter species. The distinction between the new species and other known species within the genus is specified in the key below.