Wieseria bicepes, Jia & Huang, 2020

Jia, Susu & Huang, Yong, 2020, Wieseria bicepes sp. nov. (Nematoda: Oxystominidae) from the South China Sea, Zootaxa 4722 (4), pp. 389-394 : 390-393

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 .

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).

Figures

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.