Dorylaimopsis brevispiculata, Gagarin, Vladimir G., 2013

Gagarin, Vladimir G., 2013, Four new species of free-living marine nematodes of the family Comesomatidae (Nematoda: Araeolaimida) from coast of Vietnam, Zootaxa 3608 (7), pp. 547-560 : 557-560

Dorylaimopsis brevispiculata sp. n.

( Fig.5 , Table 5 )

Type specimens. Holotype male, inventory slide no. 102 /7 deposited in the collection of the helminthological museum of the Institute of Ecology and Evolution, Center of Parasitology, Russian Academy of Sciences, Moscow, Russia. All paratype slides deposited in the nematode collection of the Institute of Ecology and Biological Resources, Vietnamese Academy of Science and Technology, Hanoi, Vietnam.

The habitat and locality. South China Sea, littoral zone of the coast of Vietnam, Tea Co. Latitude: 21º25.712’–21º27,124’. Longitude: 107º58.952’–108º02.124’. Depth 1.0–3.0 m, sand, salinity 29.1–29.5 ‰. Collected in March 2010.

Description. Male. Body slender, medium-sized, tapering towards both extremities. Cuticle marked by transverse rows of fine punctations. Lateral differentiation consists of three longitudinal rows of larger dots, beginning just posterior to amphidial fovea, extending down almost to base of pharynx and then taking the form of a series of coarse dots in two longitudinal rows terminating in the cloacal area. Lateral differentiation 7–8 µm wide at mid-body, 11–13% of corresponding body diameter. Punctaation: at tail in three longitudinal rows of dots. Somatic setae rare and sparse, 3–4 µm long. Head slightly isolated from the rest of body. Inner labial sensillae in the shape of papillae. Outer labial sensillae and cephalic sensillae in the shape of thin setae, with both circles of setae placed close together. Four cephalic setae 8.0–9.5 µm long (80–90% of labial region width). Outer labial setae slightly shorter. Amphidial fovea in the shape of a spiral with 3.0 turns and occupying about 70% of corresponding body width. Buccal cavity (stoma) in the shape of a cuticularized tube 18–23 µm long (2.0–2.2 labial region width), with three triangular teeth located at the anterior end. Pharynx widening towards its base, but without distinct bulb. Renette 27– 45 x 18–23 µm size, located at the level of anterior end of intestine. Excretory pore posterior to nerve ring. Two testes, opposite and outstretched. Spicules paired, equal, strongly arcuate, 59–68 µm long, 2.0–2.2 cloacal body diameter. Proximal ends slightly cephalated and with short median cuticularized strip. Ventral apophysis or joint line at middle of spicules absent.

Gubernaculum with two caudally-dorsally directed apophyses 20–27 µm long. Precloacal supplements not observed. Tail slender, with rather broad, conical anterior portion and rather narrow cylindrical posterior portion, the latter 0.4–0.5 times as long as anterior conical portion. Tail with numerous conical setae. Tail tip slightly enlarged, with three subterminal seta 9–11 µm long. Caudal glands and spinneret present.

Female: Similar to male in general characteristics. Structure of cuticle and anterior body end as in male. Cuticle marked by transverse rows of fine punctuations. Lateral differentiation at the level of pharynx and at tail consisting of three longitudinal rows of coarse dots and along the rest of the body in two longitudinal rows of dots. Inner labial sensillae in the shape of papillae and outer labial and cephalic sensillae in the shape of thin setae. Cephalic setae 80–85% of labial region width. Amphidial fovea in the spiral-shaped with 3.0 turns and occupying 50–55% of corresponding body width. Stoma in the shape of cuticularized tube 20–22 µm long and armed with three triangular teeth at the anterior end. Pharynx widening towards base. Rectum 0.8–1.1 times as long as anal body diameter. Reproductive system didelphic, amphidelphic; ovaries homodromous. Anterior ovary situated to right sides of intestine, posterior ovary to left side of intestine. Vulva in the shape of transverse slit, lips not cuticularized and not protruding outside the body contour. Vagina straight and short. Both uteri spacious, filled with numerous spermatozoa and elongate-spherical spermatheca 35– 36 x 31–34 µm in size. One mature female observed with single egg 50 x 48 µm in size. Tail slender, comparatively long, its anterior portion conical, then gradually narrowing, thin, with short terminal swelling. Tail tip with subterminal setae. Caudal glands and spinneret present.

Differential diagnosis. Dorylaimopsis brevispiculata sp. n. is morphologically close to D. turneri Zhang, 1992 and D. coomansi Muthumbi, Soetaert & Vincx, 1997 . It differs from both species in the shape of the outer labial sensillae (long setae vs papillae in D. turneri and D. coomansi ) and absence of precloacal supplements in males. It also differs from the former in the pattern of lateral differentiation of the cuticle and the shape of amphidial fovea (spiral with 3.0 turns vs 2.5–2.75 turns in D. turneri ) (Zhang, 1992). D. brevispiculata sp. n. differs from D. coomansi in the pattern of cuticular lateral differentiation, the shape of amphidial fovea (spiral with 3.0 turns vs spiral with 2.5 turns in D. coomansi ) and slenderer tail in males (cʹ = 3.6–4.3 vs cʹ = 3.2–3.4 in D. coomansi ) (Muthumbi, Soetaert & Vincx, 1997).

Figures

FIGURE 5. Dorylaimopsis brevispiculata sp. n. A: Entire male; B: Entire female; C: Male head; D: Cardial region of male; E: Spicular apparatus; F: Male tail; G: Female tail. Scale bars: A, B— 150 µm; D— 70 µm; G— 50 µm; F— 40 µm; C— 15 µm.

Tables

TABLE 5. Morphometrics of Dorylaimopsis brevispiculata sp. n. All measurements are in µm and the form: mean + standard deviation (range)

Character	Holotype male	Paratypes
		10 males 5 females
L	1470	1471 + 106 (1234–1620) 1715 + 56 (1607–1758)
a	34	33 + 4 (25–37) 27 + 4 (25–31)
b	7.2	7.4 + 0.4 (6.4–8.0) 8.3 + 0.5 (7.3–8.7)
c	12.6	12.0 + 0.8 (10.5–13.6) 12.7 + 0.4 (11.9–13.2)
c’	4.3	4.0 + 0.2 (3.6–4.3) 3.7 + 0.2 (3.4–3.9)
V %	–	– 49.2 + 1.2 (47.4–50.9)
Labial region width	10.0	10.5 + 0.5 (10.0–11.0) 12 + 0.5 (11–12)
Cephalic setae length	8.0	8.8 + 0.5 (8.0–9.5) 10 + 0.5 (9.0–10.0)
Stoma length	21	21 + 2 (18–23) 21 + 1 (20–21)
Amphidial fovea diameter	8.0	8.0 + 1.5 (7.5–9.0) 7.5 + 1.5 (7.0–8.0)
Oesophagus length	205	198 + 7 (191–209) 206 + 5 (486–214)
Distance from posterior end of pharynx to vulva	–	– 638 + 33 (578–675)
Distance from posterior end of pharynx to cloaca	1148	1155 + 101 (923–1298) –
Distance from vulva to anus	–	– 736 + 38 (680–788)
Body width	43	46 + 5 (38–60) 63 + 5 (27–34)
Anal (cloacal) body diameter	29	29 + 2 (27–32) 36 + 2 (34–40)
Spicules length (along arc)	59	63 + 4 (59–68) –
Dorsal apophysis of gubernaculum length	23	24 + 2 (20–27) –
Tail length	117	118 + 5 (128–140) 135 + 1 (131–137)