Cobbia heterospicula, Wang & An & Huang, 2018

Wang, Chunming, An, Liguo & Huang, Yong, 2018, Two new species of Xyalidae (Monhysterida, Nematoda) from the East China Sea, Zootaxa 4514 (4), pp. 583-592 : 587-591

Cobbia heterospicula sp. nov.

( Figs 3-4 )

Type material. Four males and one female were measured and studied. Holotype male on slide DH12-387-5; female on slide DH12-332-1; additional males on slides DH12-434-2, DH12-433-2, DH12-513-2.

Type locality and habitat. Sublittoral zone in the East China Sea. Holotype male comes from station DH3-8, 30° N, 126° E, water depth of 79 m. Muddy with a small fraction of sand sediment.

Additional specimens come from station DH3-3, 30°N, 123°29´E, water depth 69 m; DH4-3, 29° 5´N, 123°47´E, water depth 79 m; DH5-1, 28° 27´N, 122°10.4´E, water depth 43 m. Muddy with a little sand sediment fraction.

Etymology. The species name refers to the unequal size of the spicules.

Measurements. Table 2.

Description. Male. Body short and slender, 987–1094 µm long. Maximum diameter 16–19 µm. Anterior body slightly truncated and posterior body filiform. Buccal cavity funnel-shaped, with one slightly cuticularized dorsal tooth and two small subventral teeth. Head blunt, weakly set off. Six inner labial setae setiform. Six outer labial setae (7–9.4 µm) and four cephalic setae (4–4.5 µm) arranged in one circle. Somatic setae absent. Amphids circular, 4.7–6.5 µm in diameter (41–60% of corresponding body diameter), 21–29 µm (4.5–6.5 times the head diameter) from the anterior body end. Pharynx cylindrical, 142–152 µm long, posterior part widens but without forming a real bulb. Nerve ring 58–83 µm from the anterior body end, 40–54% of the pharynx length. Excretory glands and excretory pore unobserved. Cardia conical, 5 µm long. Tail conico-cylindrical, 227–307 µm long (13– 18 times the anal body diameter), cylindrical part filiform (167–245 µm, 74–80% of tail length).

Gonads diorchic and opposed. Anterior testis to the left of the intestine and posterior testis to the right of the intestine. Spicules curved, paired but differing in length, right spicule 27–33 µm and left spicule 15–20 µm (measured along arc). Gubernaculums are parallel to the distal part of spicules, with tapering dorsal apophysis.

Female. Similar to males in most respects, but with a longer tail. Reproductive system monodelphic, prodelphic. A single ovary, anteriorly outstretched, situated to the right of the intestine. Vagina short, bending anteriorly. Spermatheca not seen. Vulva a transverse slit-like structure, located at approximately the midbody, 603 µm (50.4%) from the anterior body end.

Differentiation diagnosis and discussion. Cobbia heterospicula sp. nov. is characterized by a short and slender body, buccal cavity with one dorsal and two small subventral teeth, amphids located far from the anterior body end, conico-cylindrical tail with a long filiform portion, paired spicules of different sizes, and gubernaculums with dorsal apophysis.

C. heterospicula sp. nov. can be easily distinguished from the other species by its unequally sized spicules and slender body. Anterior sensilla configuration and tooth composition are two diagnostic features in Cobbia (Lo Russo & Pastor de Ward 2012) , and this new species belongs to the group of species that have anterior sensilla configuration of 6+10, one large dorsal tooth and two subventral teeth.

C. heterospicula sp. nov. resembles C. caledonia in its body length, anterior sensilla configuration, large amphids (0.41–0.6 times the corresponding body diameter), and position of amphids (more than two times the head diameter from the anterior body end) but differs in its spicules without proximal cephalation, gubernaculums with dorsal apophysis and tail shape (conico-cylindrical with a long filiform portion vs. conical) ( Warwick & Platt 1973).

Gubernaculum apophysis was observed in C. heterospicula sp. nov., C. truncata and C. sinica . However, the apophysis in C. sinica is small, and in C. truncata , the distal end is blunt or slender ( Huang & Zhang 2010, Wieser 1959). The new species differs from C. truncata in its shorter body length (1.06–1.19 mm vs. 1.45–1.59 mm), cuticle pattern (finely striated vs. coarsely annulated), anterior sensilla configuration (6+10 vs. 6+12), teeth composition (one dorsal and two small subventral teeth vs. three teeth of equal size), absence of cervical setae and somatic setae, and longer tail (17 anal body diameters long vs. 5.8 anal body diameters long) ( Wieser 1959).

Figures

FIGURE 3. Cobbia heterospicula sp. nov. A. Lateral view of male anterior end, showing buccal cavity; B. Lateral view of male anterior end, showing cephalic seta and amphid; C. Lateral view of male posterior portion, showing spicules; D. Lateral view of male posterior portion, showing gubernaculums. Scales: A–D=20 µm.

FIGURE 4. Cobbia heterospicula sp. nov. A. Lateral view of male anterior end, showing buccal cavity and amphids; B. Lateral view of male posterior body, showing tail; C. Lateral view of male anterior end, showing pharyngeal region; D. Entire view of female body, showing vulva; E. Lateral view of spicules and gubernaculums. Scales: A=10 µm, B=50 µm, C=30 µm, D=50 µm, E=20µm.