Draconema andamanense, Kito, Kenji & Chatterjee, Tapas, 2012

Kito, Kenji & Chatterjee, Tapas, 2012, New species of the genera Draconema Cobb, 1913 and Paradraconema Allen & Noffsinger, 1978 (Nematoda: Draconematidae) from the Andaman Islands, Indian Ocean, with keys to the species, Zootaxa 3575, pp. 78-88 : 79-83

Draconema andamanense sp. nov.

( Fig.1 )

Type specimens. Holotype: male ( ZIHU 4256). Paratypes: four males ( ZIHU 4257–4260) and five females ( ZIHU 4261–4265). Coll. T. Chatterjee, December 2005.

Type locality and habitat. Wandoor (11°40.55’N, 92°45.12’E), South Andaman, Andaman Islands; intertidal sediments among macroalgae ( Halimeda opuntia ): holotype ZIHU 4256 and paratypes ZIHU 4257, 4265. Burmanalla (11°33.45’N, 92°43.78’E), South Andaman, Andaman Islands; intertidal sediments among mixed macroalgae: paratypes ZIHU 4258–4264.

Measurements. Table 1.

Description. MALE. Body shape characteristic for the genus ( Fig. 1 A). Swollen pharyngeal region 11.8 (11.3–12.4; 11.9±0.4)% of total body length; rest of trunk almost cylindrical, slightly narrowed at middle; tail gradually tapering to conical tip; greatest body diameter at swollen pharyngeal region. Cuticle annulated except for head capsule and tail end. Anteriormost 12–13 (11–14) annules of swollen pharyngeal region ( Fig. 1 B) differentiated, large and ornamented with subcuticular markings and vacuoles, 2.8 (2.2–2.8) μm wide; annules 1.7 μm wide at middle of swollen pharyngeal region and 1.1–1.5 μm wide in remaining body region; annules S-shaped laterally at midbody. Somatic setae arranged in eight longitudinal rows (four sublateral, two subventral, two subdorsal) except for swollen pharyngeal region with many short and long setae densely and irregularly distributed and tail with four rows (two subventral and two subdorsal). Most somatic setae hair-like with broadened base, longest in pharyngeal region, 54 (37–54) μm long; some short, truncated setae (3–7μm long) intermingled with rows of hair-like setae and posterior adhesion tubes.

Head capsule ( Fig. 1 C) well cuticularized, 18.3 (17.3–22.1; 20.2±2.2)% length of swollen pharyngeal region, posteriorly ornamented with faint subcuticular markings. Labial region 4 (4–6) μm in length and 11 (9–13) μm diameter, with six short inner labial setae (4–7 μm long) on lips and a circle of six outer labial setae at posterior end of labial region (4–5 μm long). Cephalic setae not distinguished from subcephalic or cervical setae densely located at anterior head capsule. Amphids elongate loop-shaped, ventral arm longer, extending to near first annule, 15/15 (13–18) μm long and 10/10 (10–12) μm wide. Twelve CAT with enlarged base, arranged in two transverse rows dorsally between amphids, longest tube 31 (31–32) μm long. Stoma narrow, unarmed; yellow-brownish coarse granules gathered near labial region. Pharynx dumbbell-shaped, with enlarged corpus and well developed posterior bulb, separated by isthmus, 30 (26–30) μm diameter near middle of posterior bulb. Cardia narrow, about 16 (13–18) μm long. Nerve ring obscure, surrounding isthmus of pharynx, about 0.6 (0.5–0.6) pharyngeal length from anterior body end. PAT broadened basally, with bell-shaped ends, arranged in four longitudinal rows ( Fig. 1 D). SlAT in two rows, each consisting of nine adhesion tubes (A) and four intermingled long setae (S) in order A–A–S–A–A–S–A–A–S–A–A–S–A from anterior; anteriormost and posteriormost tubes 59 (49–59) μm and 42 (37–44) μm long, respectively. SvAT in two rows each consisting of 11 (10–11) tubes, the two rows almost converging posteriorly; posterior five tubes of each row located alternately near ventral line with a wider spacing than that in anterior tubes; anteriormost and posteriormost tubes 43 (41–49) μm and 30 (25–30) μm long, respectively. Region with PAT (between anteriormost and posteriormost SvAT) 13.6 (12.3–15.0; 13.8±1.1)% of total body length.

Reproductive system with single outstretched testis; anterior end located at about 14 (14–40)% of body length from anterior body end. Spicules ( Fig. 1 E) arcuate, proximally with knob-like cephalation, 2.1/2.2 (1.9–2.2; 2.1±0.1) abd long, about 4–5 μm wide at middle. Gubernaculum somewhat wavy, 47/42 (37–47; 43±2.4)% of spicule length; with weakly cuticularized distal dilation, proximal end curved anteriorly. Cloacal flap short. Four cloacal setae present; two short inner setae with very enlarged base, unevenly tapered, 6–7 (4–10) μm long; two outer setae uniformly tapering, anterior seta longer than posterior one, 15 (12–16) μm and 12 (9–13) μm long, respectively.

Tail cylindro-conoid, gradually tapering to non-annulated tail end, 4.4 (3.9–4.4; 4.1±0.20) abd long. Six somatic setae on each side of annulated tail region, three subventral and three subdorsal; middle subdorsal seta longer, 21 (16–22) μm long. Non-annulated tail end length 0.3 (0.32–0.35) of total tail length, dorsally vacuolated, with six setae on each side; long subdorsal seta close to last complete annule, 35 (29–37) μm long; short hair-like seta and short truncate seta closely situated at middle of lateral side, 45/44 (36–49; 42.3±4.1)% of non–annulated end from last complete annule. Caudal glands extending to 4 (3.1–4.5) abd anterior to cloaca.

FEMALE. Body similar to male in most respects ( Fig. 1 F). Greatest body diameter mostly at swollen pharyngeal region, sometimes around level of vulva. Amphids generally uni-spiral, sometimes loop-shaped to unispiral, 9/11 (9–14) μm long and 10/10 (10–12) μm wide ( Fig. 1 G, H). Longest somatic seta in pharyngeal region, 48 (44–59) μm long. PAT arranged in four longitudinal rows ( Fig. 1 I), two sublateral rows of 14/14 (14/14–15) tubes and two subventral rows of 13/12 (12–14) tubes; short truncate setae intermingled with sublateral adhesion tubes. Region with PAT 15.2 (13.9–16.6; 15.3±1.1)% of total body length.

Reproductive system amphidelphic. Ovaries on left side of intestine, reflexed to left side, anterior branch length to flexure 28 (9–28) and posterior branch length to flexure 17 (9–17)% of total body length. Vulva slightly protruded, located near midbody, with two short paravulval setae (5–6 μm long) located a short distance lateral to the vulva.

Tail cylindro-conoid, gradually tapering to non-annulated tail end, 4.6 (4.6–5.4; 5.0±0.3) abd long. Four or five somatic setae on each side of annulated tail region, second subdorsal seta longer, 24 (21–24) μm long. Nonannulated end length 0.4 (0.42–0.46) of total tail length, with five setae in each side; longest subdorsal seta 42 (32–42) μm long; short truncate seta situated laterally at 47/43 (43–58; 52.0 ± 4.9)% of non-annulated end from last complete annule. Caudal glands extending to 2.4 (2.4–6.0) abd anterior to anus.

Etymology. Named after the type locality, the Andaman Islands.

Differential diagnosis. Draconema andamanense sp. nov. is characterized in the genus by the following features: body length (960–1291 µm); anteriormost 11–14 annules of swollen pharyngeal region differentiated; spicules with knob-like proximal cephalation; number of posterior adhesion tubes (SlAT, 9 in male and 14–15 in female; SvAT, 10–11 in male and 12–14 in female); gubernaculum with weak distal dilation (0.4–0.5 spicule length); subventral cloacal setae unevenly tapered; tail length (3.9–4.4 abd in male and 4.6–5.4 abd in female); and non-annulated tail end length 0.3–0.4 and 0.4–0.5 of tail length in male and female.

Draconema has so far consisted of the following nine species ( Venekey et al., 2005): D. antarcticum Allen & Noffsinger, 1978 , D. brasiliense Venekey, Lage & Da Fonsêca-Genevois, 2005 (lapsus brasilensis; Rho et al., 2011), D. cephalatum Cobb, 1913 , D. chilense Allen & Noffsinger, 1978 , D. claparedii (Mechnikov, 1867) , D. fluminense Venekey, Lage & Da Fonsêca-Genevois, 2005 (lapsus fluminensis; Rho et al., 2011), D. haswelli (Irwin-Smith, 1918) , D. japonicum Kito, 1976 , and D. ophicephalum (Claparéde, 1863) .

Of the known species, D. andamanense sp. nov. clearly differs from D. chilense and D. ophicephalum by the number of sublateral posterior adhesion tubes (SlAT 9 vs. 14–19 in male and 14–15 vs. 18–24 in female: Allen & Noffsinger 1978, Rho & Kim 2004, Venekey et al. 2005). D. andamanense sp. nov. resembles D. brasiliense , D. cephalatum , D. japonicum , and D. fuluminense in having unevenly tapered subventral cloacal setae, as opposed to uniformly tapered setae in the remaining three species, D. antarcticum , D. claparedii , and D. haswelli . However, D. andamanense has a smaller number of subventral adhesion tubes (SvAT; 10–11 in male and 12–14 in female) than D. brasiliense , D. cephalatum , D. japonicum , and D. fuluminense (14–19 in both sexes; cf. the comparison table of species morphological features in Venekey et al. 2005).

In having a gubernaculum with peculiar distal dilation, D. andamanense is similar to D. japonicum , but the dilation of D. andamanense is weakly cuticularized and not as conspicuous as in D. japonicum . Draconema andamanense also differs from D. japonicum by the following features: rather shorter spicule (56–67 μm and 1.9–2.2 abd long vs. 61–93 μm and 2.2–3.1 abd long), longer gubernaculum (25–28 μm and 0.4–0.5 spicule length vs. 17–25 μm and about 0.3 spicule length) and longer female tail (103–114 μm and 4.6–5.4 abd long vs. 74–103 μm and 3.7–4.3 abd) ( Kito, 1976, 1979; Rho & Kim, 2004). Draconema andamanense is similar to D. cephalatum in general morphometric features but differs from it in having a simple gubernaculum with no distal dilation and a larger number of SvAT (14–18 tubes) ( Cobb, 1913, 1929; Allen & Noffsinger, 1978).

The two Brazilian species D. brasiliense and D. fluminense are characteristic in the genus by having larger numbers of anteriormost large annules (15–16 vs. 11–14 in the other species). In addition, D. andamanense is distinguished from the Brazilian species by gubernaculum length (25–28 μm vs. 34–44 μm in D. brasiliense and 31–44 μm in D. fluminense ) and tail length (3.9–4.4 abd in male and 4.6–5.4 in female vs. 2.5–3.4 and 3.0– 4.1 in D. brasiliense , 2.5–3.7 and 2.3–4.5 in D. fluminense ). Venekey et al. (2005) described that the males of the Brazilian species have the gubernaculum with either a reduced lateral wing ( D. brasiliense ) or a lateral wing ( D. fluminense ). No comparison of this feature is possible, however, because there was no additional information about the feature in their original text or figures.

Draconema andamanense sp. nov. is the second member of the genus found in India. The first, D. cephalatum , was recorded by Rao (1980, 1987, 1988) in a species list of meiofauna from a faunal survey of the Andaman and Nicobar Islands—the same islands where D. andamanense was found. The general morphological similarity of the species and the similarity of collection locations makes it possible that the earlier record was in fact D. andamanense sp. nov..

Figures

FIGURE 1. Draconema andamanense sp. nov. Male (A – E, holotype ZIHU 4256): A) Entire body. B) Swollen pharyngeal region. C) Head region, surface view. D) Posterior region. E) Spicule and Gubernaculum. Female (F, G, I, ZIHU 4262; H, ZIHU 4261): F) Entire body. G, H) Amphid. I) Posterior region, left side view; some SvAT missing. Scales: A, F, 50 µm; B, D, I, 20 µm; C, E, G, H, 10 µm.