Draconema ophicephalum ( Claparède, 1863 ), Claparede, 1863

Fedyaeva, Maria A., Neretina, Tatjana V., Konovalova, Olga P. & Tchesunov, Alexei V., 2016, Two known and one new species of Draconematidae and Epsilonematidae (Nematoda, Desmodorida) from the White Sea, North Russia, Zootaxa 4121 (4), pp. 383-411 : 387-392

Draconema ophicephalum ( Claparède, 1863)

Figs 1–3, Table 2 (morphometrics)

Material. Ten males and ten females.

Locality. White Sea (Northern Russia), Karelian Coast of the Kandalaksha Bay, vicinity of the White Sea Biological Station, Velikaja Salma Strait between the Veliky Island and Kindo Peninsula (66°33'N, 33°06'E), depth 2–5 m, brown and red algae. 18–27 August 2013.

Description. Body swollen in the middle of pharyngeal region and strongly narrowed just posteriorly at the level of cardia and anterior-most intestine. Male bodies slightly slimmer than that of females. Most specimens bent dorsally in anterior half of the body. Female body noticeably widened in region of the reproductive organs. Body cuticle distinctly annulated along the entire body, thicker in the pharyngeal region and thinner posterior to the cardia. Anterior-most head cuticle smooth, forming rostrum. Length of the rostrum 15–39 µ m in males and 17–33 µ m in females. Anterior 12–14 cuticular annules of the pharyngeal region enlarged (three annules in 10 µ m) and marked with tiny irregular vacuoles along the midline of each annule while remaining posterior annules of the body are 2–3 times more narrow (8–9 annules in 10 µ m) and look homogeneous.

Small mouth opening covered with six rugose lips. Labial region encircled with a tight and narrow hexagonal furrow and then with a wider radially rugose (crumpled) zone ( Fig. 3 D). Six short (4–5 µ m) inner labial setae situated in the furrow. Six outer labial setae 5–6 µ m long located at the outer margin of the rugose zone. Four cephalic setae 16–18 µ m long located at level of anterior edge or middle part of amphideal fovea. Numerous somatic (subcephalic) setae on the rostrum mask cephalic setae, hence the cephalic setae may be difficult to distinguish. Amphideal fovea situated at the base of the rostrum in latero-dorsal position. Amphideal fovea large, loop-shaped, dorsal arm slightly longer than ventral, with no difference in shape between males and females. Width of the amphideal fovea 1.6–3.2 µ m in males and 1.6–2.6 µ m in females.

There are about 290–300 various non-modified and modified somatic setae along the body. Cephalic adhesive tubes (CATs) long and wide setae bent anteriorly, with bulb-shaped bases and slightly modified tips, situated dorsally on the rostrum. Twelve CATs located in six longitudinally arranged pairs, two dorsal pairs, two subdorsal and two laterodorsal pairs, posterior tube longer than anterior one in each pair ( Fig. 3 B). Non-modified thin and flexible somatic setae arranged in eight irregular rows along the body. Longest setae located on pharyngeal region (up to 55 Μ m in males, up to 51 Μ m in females); length of most somatic setae on remainder of body nearly equal in length (32–45 Μ m in males, 30–45 Μ m in females). Six pairs of setae on annulated part of the tail and 3–4 pairs on non-annulated terminal cone of the tail. Posterior adhesive tubes (PATs) present as wide and stiff slightly bent, with bulb-shaped bases and cup-shaped tips. The PATs arranged in two subventral and two latero-ventral rows on the posterior body, anterior to anus. Length of PATs decreases slightly towards posterior end of rows. There are four non-modified hair-like somatic setae inserted in subventral PAT rows; comparable to PATs in length but thinner. Two anterior-most somatic setae in these rows slightly shorter than adjacent PATs; two posterior-most somatic setae slightly longer than adjacent PATs.

Buccal cavity small and unarmed. Some orange pigment granules present around the stoma. Pharynx dumbbell-shaped, swollen anteriorly and posteriorly, with a narrowing (isthmus) between the swellings in the middle part of the pharynx.

One anterior testis located ventrally to the intestine. Spicules slender, elongate, slightly arcuate, distally pointed and proximally with a capitulum. Gubernaculum a small bar. Four pairs of anal setae: two pairs (short and long) anterior to anus and two pairs (short, conical and long) posterior.

Ovaries antidromously reflexed and located ventrally to the intestine.

Tail elongate conical, non-annulated terminal part (terminal cone) 28–30% of the total tail length in males and 37–42% in females. Caudal glands extended a little to precaudal region.

Diagnosis. Draconema . Body length 998–1676 µ m in males and 1097–1700 µ m in females; a 16.7–28.6 in males and 13.3–16.8 in females. Anterior 12–14 cuticular annules of the pharyngeal region enlarged and marked with tiny irregular vesicles, while posterior annules of the body two to three times narrower and homogeneous. Longest somatic setae (up to 57 µ m) located on pharyngeal region. Amphideal fovea loop-shaped, dorsal arm slightly longer than ventral arm. Twelve cephalic adhesive tubes located in six longitudinally arranged pairs. The posterior adhesive tubes arranged in two lateroventral (12–19 in males and 12–22 in females) and two subventral (14–19 in males and 16–21 in females) rows on the posterior body before anus. Spicules 70–93 µ m, gubernaculum 37–62 µ m long.

Discussion. All Draconema species have overall similarity and differ from one another in fine details, particularly in number of sublateral adhesion tubes. The White Sea species is close to the re-description of D. ophicephalum by Allen & Noffsinger (1978), except for a slight difference in the length of the last subventral adhesive tubes in females (27–31 µm vs 21–26 µm). We propose that D. ophicephalum should be re-described because it has been collected in a new region (White Sea) remote from the type locality (Mediterranean).

Since the synonymization of Allen & Noffsinger (1978) and Decraemer et al. (1997), the known geographic range of D. ophicephalum is wide, including the Mediterranean, Black Sea, English Channel, North Sea, Baltic Sea, Greenland, and Barents Sea. Here, the range is extended to the north-east with the finding of the species in the White Sea.

Figures

FIGURE 3. Draconema ophicephalum, Scanning Electron Micrographs. A: male, entire; B: female head, dorsal view with cephalic adhesive tubes; C: male head, apical view; D: male labial region; E: posterior adhesive tubes; F: female, vulva region. Scale bars: A 100 Μ m; B, C, E, F 10 Μ m; D 3 Μ m.

Tables

TABLE 2. Morphometrics of Draconema ophicephalum.

Character	Males, n=10				Females, n=10
	min-max	mean	SD	CV, %	min-max mean	SD	CV, %
L, µ m	998 1676	1337	261	19.5	1097 1394 1245	106	8.51
a	17.1 26.7	21.9	3.89	17.7	13.3 16.8 15.1	1.02	6.72
b	10.4 12.1	11.3	0.52	4.61	9.38 12.1 10.7	0.81	7.55
c	7.37 11.3	9.35	1.22	13.0	8.19 10.5 9.36	0.75	8.03
V,%					22.6 30.2 26.4	2.77	10.5
c'	2.32 5.41	3.86	0.85	21.9	4.14 5.22 4.68	0.33	7.10
điam.c.s, µ m	17.0 33.0	25.0	4.36	17.4	20.0 30.0 25.0	3.48	13.9
điam.am., µ m	28.0 50.0	39.0	5.74	14.7	33.0 46.0 39.5	3.92	9.93
điam.n.r., µ m	64.0 79.0	71.5	4.95	6.93	71.0 82.0 76.5	3.72	4.86
điam.ant.swell., µ m	67.0 83.0	75.0	5.07	6.76	71.0 87.0 79.0	5.06	6.40
điam.ca., µ m	37.0 49.0	43.0	4.99	11.6	34.0 50.0 42.0	4.53	10.7
điam.miđb., µ m	41.0 72.0	56.5	10.5	18.6	46.0 78.0 62.0	9.98	16.1
điam.ani, µ m	27.0 56.0	41.5	8.07	19.4	26.0 33.0 29.5	2.39	8.12
wiđth of pharynx anterior to nerve ring, µ m	28.0 66.0	47.0	10.9	23.3	32.0 42.0 37.0	2.91	7.8
wiđth of pharynx at nerve ring, µ m	19.0 27.0	23	3.18	13.8	19.0 29.0 24.0	3.39	14.1
terminal bulb wiđth, µ m	39.0 51.0	45	3.63	8.06	40.0 58.0 49.0	5.09	10.4
terminal bulb length, µ m	40.0 69.0	54.5	9	16.5	44.0 69.0 56.5	7.04	12.4
Anterior đorso lateral CATs, µ m	18.0 28.0	23	3.17	13.7	19.0 28.0 23.5	3.47	14.7
Posterior đorso lateral CATs, µ m	24.0 35.0	29.5	3.16	10.7	23.0 34.0 28.5	3.24	11.3
Anterior subđorsal CATs, µ m	23.0 27.0	25	1.51	6.04	20.0 28.0 24.0	2.57	10.7
Posterior subđorsal CATs, µ m	25.8 33.0	29.4	2.49	8.46	26.0 32.0 29.0	2.45	8.45
Number of left lateroventral PATs	12 19	15.5	1.75	11.3	12 22 17.0	2.78	16.3
Number of left subventral PATs	15 19	17.0	1.32	7.74	16 21 18.5	1.41	7.64
Number of right lateroventral PATs	12 18	15.0	1.69	11.2	13 22 17.5	2.67	15.3
Number of right subventral PATs	14 19	16.5	1.73	10.5	16 20 18.0	1.29	7.15
Anteriormost left lateroventral PAT, µ m	48.0 65.0	56.5	5.06	8.95	47.0 63.0 55.0	5.14	9.35
Posteriormost left lateroventral PAT, µ m	32.0 47.0	39.5	4.69	11.8	30.0 46.0 38.0	5.46	14.3
Anteriormost left subventral PAT, µ m	30.0 53.0	41.5	7.06	17.0	39.0 49.0 44.0	3.76	8.54
Posteriormost left subventral PAT, µ m	25.0 47.0	36.0	6.25	17.3	27.0 31.0 29.0	1.27	4.38
Spicule length along arc, µ m	70.0 93.0	81.5	7.20	8.83
Gubernaculum length, µ m	15.0 24.0	19.5	2.63	13.5
Tail terminal cone, µ m	37.0 62.0	49.50	8.25	16.6	39.0 59.0 49.0	6.83	13.9