Wieseria bicepes sp. nov. (Nematoda: Oxystominidae) from the South China Sea Author Jia, Susu Author Huang, Yong text Zootaxa 2020 2020-01-15 4722 4 389 394 journal article 24332 10.11646/zootaxa.4722.4.8 f36c5d06-ad05-4b3c-8ded-ebb9fa8afd72 1175-5326 3609627 7FA56DFB-C6E4-41B7-A65B-FB362C8FDDF2 Wieseria bicepes sp. nov. ( Figs 1–2 ) Type material. Holotype was collected from Station NH2017-8, on the slide NH-8-157-3. Additional material. Male #2 and juvenile were collected from Station NH2017-8 and Station NH-W7, on slides NH-8-158-3 and NH-W7-22-4, respectively. Type locality and habitat. Seabed in the South China Sea. Station NH 2017-8: 114º45′29″E , 19º51′43″N , water depth 795 m , clay sediment . Additional locality and habitat. Seabed in the South China Sea. Station NH-W7: 115º52′12″E , 21º7′12″N , water depth 273 m , clay sediment with sand and nodules. Etymology. The species name refers to its bifurcate tail tip. Measurements. Table 1 . TABLE 1. Individual measurements (in µm) of Wieseria bicepes sp. nov.

Characters	Holotype	♂ #2	Juvenile
Total body length	3149	3160	1013
Maximum body diameter	23.3	21.5	18.5
Head diameter	6	6.5	4.5
Length of inner labial setae	6	6.5	5.8
Length of outer labial setae	6	5.5	5.5
Length of cephalic setae	6.1	7	5.9
Amphideal fovea length	10	9.5	7.8
Amphideal fovea width	6.3	6.3	5.3
Amphideal foveas from anterior end	24.2	19.3	24.5
Nerve ring from anterior end	149	138	102
Excretory pore from anterior end	92	78	75
Body diameter at nerve ring	18.1	17.6	13.7
Pharynx length	356	339	214
Body diameter at the base of pharynx	20.3	20.1	17.1
Spicule length as arc	12.5	15	-
Cloacal or anal body diameter	14.6	14.5	14.5
Tail length	160	154	108
a	135	147	54.7
b	8.9	9.3	4.7
c	19.6	20.5	9.4

FIGURE 1. Wieseria bicepes sp. nov. (A) anterior end of male, showing labial and cephalic setae, amphideal fovea; (B) anterior end of juvenile; (C) pharyngeal region of male; (D) spicule and precloacal spine; (E) posterior end of male, showing spicule, precloacal spine and bifurcate tail tip; (F) tail end of juvenile, showing caudal glands and bifurcate tail tip. FIGURE 2. Wieseria bicepes sp. nov. (A), (B) anterior end of males, showing labial and cephalic setae, amphideal fovea; (C) cloacal region of male, showing spicule and precloacal spine; (D) tail end of male, showing bifurcate tip; (E) posterior end of juvenile, showing caudal glands and bifurcate tail tip; (F) anterior end of juvenile. Scale bars: A, B, C, E, F 10 µm; D 20 µm. Description. Males. Body slender, tapering towards anterior and posterior ends, greatest body diameter at the middle of body. Cuticle smooth. Somatic setae not observed. Twelve labial sensilla setiform. Inner labial setae and outer labial setae nearly equal in length, about 6 μm (1 head diameter) long. Four cephalic setae just behind the outer labial setae and are similar to outer labial setae in length. Amphideal fovea oblong with double contours and a handle-like protrusion at the base, about 0.5 corresponding body diameter wide, located at 24 μm from anterior end. Buccal cavity tiny, narrow slit shaped. Pharynx slender, cylindrical and slightly widened at base, not forming posterior terminal bulb. Cardia conical, surrounded by intestine tissue. Nerve ring situated about two-fifths of pharynx length from anterior end. Excretory pore opening at about one-fourth of pharynx length, 92 μm from anterior end. Tail conical gradually becoming filiform, 10.9 cloacal body diameter, tip bifurcate. Caudal setae short and sparse, 2.3–2.8 μm long. Three caudal glands present in conical region of tail. Two opposed, outstretched testes, anterior branch on left of intestine and posterior branch on right. Spicules slightly curved, with cephalated proximal end and tapered distal end, equal to 0.86–1.03 cloacal body diameter in length. Gubernaculum absent. One precloacal ventral spine 2.5 μm long, located 3 μm anterior to the cloacal open- ing. Juvenile. Similar to males in the most morphological characteristics except relatively wide body (small a value), tail constricted sharply to filiform at junction of conical and cylindrical sections, and tail with three distinct caudal glands. Female not found. Differential diagnosis and Discussion. Wieseria bicepes sp. nov. is characterized by three circles of anterior sensilla almost equal in length; four cephalic setae closely adjacent to outer labial setae; oblong amphideal fovea with double contours and a handle-like protrusion at the base; tail tip bifurcate; spicules slightly curved with cephalated proximal end and tapered distal end; gubernaculum absent. Wieseria biceps sp. nov. belongs to the Group III which has tail with a bifurcate tip (Yu and Xu, 2017). The species is easily distinguished from the congeneric species by the main features of tail with a bifurcate tip and cephalic setae closely adjacent to labial setae. The present species is similar to W. scotlandica Zhang 1983 and W. hispida Vitiello 1972 in general morphological characteristics, especially in having a bifurcate tail tip. However, the present new species differs from W. scotlandica by the position of cephalic setae adjacent to the labial setae (vs far apart), absence of gubernaculum (vs present), shorter spicules (12.5–15 μm vs 20.5 μm), much shorter labial setae and cephalic setae (inner labial setae 6–6.5 μm vs 14 μm, ce- phalic setae 6–7 μm vs 10.5 μm). Moreover, the present new species differs from W. hispida in cephalic setae closely adjacent to labial setae, shorter inner labial setae and cephalic setae (6–7 μm vs 12.5 μm).