Paradraconema pachylumbus, 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 : 84-87

Paradraconema pachylumbus sp. nov.

( Fig.2 )

Type specimens. Holotype: male ( ZIHU 4266). Paratypes: three females ( ZIHU 4267–4269). Coll. T. Chatterjee, December 2005.

Type locality and habitat. Burmanalla (11°33.45’N, 92°43.78’E), South Andaman, Andaman Islands; intertidal sediments among mixed macroalgae.

Measurements. Table 2 .

Males Females

* Holotype; **“number of tubes” or “number of tubes + number of insertion of tubes taken off”; Measurements in µm, except for de Man’s ratios (a–c) and V(%).

Description. MALE. Body characteristic for the genus in general ( Fig. 2 A), except for peculiar shape of cloacal region ( Fig. 2 E). Swollen pharyngeal region 15.4% of body length; rest of trunk almost cylindrical but cloacal region remarkably enlarged towards dorsal side; tail conico-cylindrical, abruptly narrowing after enlarged cloacal region. Greatest body diameter at enlarged cloacal region. Cuticle annulated except for head capsule and tail end; annules longitudinally aerolated in anterior one-third of body; anteriormost four annules of swollen pharyngeal region somewhat differentiated, ornamented with subcuticular markings and vacuoles ( Fig. 2 B, C). Annules of swollen pharyngeal region coarse, 2.6 μm wide; subsequent annules 1.8, 1.6, 1.3 μm wide at midbody, cloacal region and near tail end, respectively; annules S-shaped laterally at midbody. Somatic setae arranged in ten longitudinal rows on non-swollen body (four sublateral, two subventral, two subdorsal, one ventral, and one dorsal), densely and irregularly distributed in swollen pharyngeal region. Most somatic setae hair-like with broadened base, sublateral rows of setae rather longer, maximum 54 μm long near midbody; ventral and dorsal setae short, sparse; short truncate setae (3–5 μm long) intermingled with hair-like setae and posterior adhesion tubes.

Head capsule ( Fig. 2 C) ornamented with faint subcuticular markings posteriorly, about length 0.2 of swollen pharyngeal region. Labial region retracted, about 12 μm diameter, with six short labial setae (3–4 μm long). Outer circle of labial setae and cephalic setae not distinguishable from subcephalic or cervical setae densely located at anterior head capsule. Amphids elongate loop-shaped, ventral arm longer, extending to near first annule, 15/14 μm long and 9/8 μm wide. CAT with enlarged base, arranged in two transverse rows of six each on dorsal side between amphids, longest tube 27 μm long. A pair of small subventral thorns (Ceph Acan-set) at posterior third of head capsule, 3–4 μm long and 2–3 μm wide. Oval-shaped eyespots prominent, 7–9 μm long and 5–6 μm wide. 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, 23 μm wide at middle of posterior bulb. Cardia short, about 5 μm long. Nerve ring surrounding isthmus of pharynx, about 0.5 pharyngeal length from anterior body end. Anterior portion of intestine very narrow, gradually expanding posteriorly. PAT with broadened bases and bell-shaped distal ends, arranged in four longitudinal rows ( Fig. 2 D), two sublateral rows (SlAT) each consisting of ten adhesion tubes (A) and two intermingled long setae (S), in order of A–S–A–A–A–A–A–A–A–S–A–A from anterior; anteriormost and posteriormost tubes 42/40 μm and 30/30 μm long, respectively. Two subventral rows of 14 adhesion tubes each; anteriormost and posteriormost tubes 36 μm and 20 μm long, respectively. Region with PAT (between anteriormost and postreriormost SvAT) 16.6% of body length.

Reproductive system with single outstretched testis; anterior end located at about 29% of body length from anterior body end. Spicules ( Fig. 2 E) arcuate, with knob-like cephalation proximally, about 1.5 abd long, 6 μm wide at middle. Gubernaculum nearly half (54/49%) spicule length, lateral dilation weakly cuticularized and thin; proximal end slightly curved anteriorly. Three short uniformly tapered cloacal setae with well-cuticularized, enlarged base located a short distance lateral to the cloaca on each side, about 5–7 μm long; two subventral setae anterior and posterior to cloaca. A pair of small precloacal Acan-set between anterior subventral cloacal setae, about 3 μm long and 2 μm wide. Cloacal flap indistinct.

Tail conico-cylindrical, abruptly narrowing after enlarged cloacal region, then gradually tapering to tip end, 3.4 abd long. Eight caudal setae (or insertions) on each side of annulated tail region, two subventral and six subdorsal; third and fourth subdorsal setae longer, fourth seta longest, 41/44 μm long; two short subdorsal setae (or insertions) close to longest seta. Non-annulated tail end 34% of tail length, vacuolated dorsally, with three short setae on both sides; sublateral seta close to last complete annule, subventral seta located 20/14%, subdorsal seta 49/45% of nonannulated end from last complete anuule. Caudal glands extending to middle of enlarged cloacal region, 1.6 abd anterior to cloaca.

FEMALE. Body similar to male in most respects except for cylindrical anal region ( Fig. 2 F). Greatest body diameter at vulva. Swollen pharyngeal region 16.4 (15.4–16.2)% of body length. Amphids ( Fig. 2 G) loop-shaped or elongated uni-spiral ( Fig. 2 H), 13/13 (13–14) μm long and 11/10 (10–11) μm wide. Ceph Acan-set 3–6 μm long and 2–4 μm wide. PAT in four longitudinal rows ( Fig. 2 I); two sublateral rows each of 13 tubes with no long setae intermingled; two subventral rows of 18/17 (16–18) tubes. Region with PAT 17.6 (17.1–17.6)% of total body length.

Reproductive system amphidelphic. Anterior ovary reflexed at about 9 (9–10)% of body length, distal end to right of uterus; posterior ovary reflexed at 12 (10–14)% of body length, distal end to left of uterus. Vulva protruded, located near midbody, with two short paravulval setae on each side (about 4 μm long in allotype ZIHU 4267).

Tail cylindro-conoid, gradually tapering to tail end, 6.2 (6.2–6.9) abd long. Eight pairs of caudal setae on annulated tail region as in male; longest subdorsal seta 44 (38–53) μm long, with two short setae nearby. Nonannulated tail end 34 (34–39)% of tail length, with two short setae (or insertions) on each side, a subventral seta located 3/8 (3–10)% of length of non-annulated end from last complete annule, and a subdorsal seta 49/46 (46–54)% of length of non-annulated end from last complete annule. Caudal glands extending to level of 3.2 abd length anterior to anus.

Etymology. The specific name pachylumbus refers to the peculiar shape of male cloacal region remarkably enlarged towards dorsal side.

Differential diagnosis. Paradraconema pachylumbus sp. nov. is characterized by the following features: peculiar body shape of male (cloacal region remarkably enlarged towards dorsal side); annules longitudinally aerolated in anterior one-third of body; elongate loop-shaped or uni-spiral amphids; prominent eyespots; spicules with proximal knob-like cephalation; gubernaculum with weak lateral dilation 25–27 μm long; a subventral pair of precloacal Acan-set; 10 SlAT and 14 SvAT in male; 13 SlAT and 16–18 SvAT in female; male tail abruptly narrowing and 3.4 abd long; long crenate anal flap in female; eight setae on annulated region of tail; and three and two setae on the non-annulated tail end in the male and female, respectively.

Paradraconema has so far consisted of ten known species which can be divided into the following two groups on the basis of the shape of the amphids in males, according to the key to species of the genus by Allen & Noffsinger (1978) and the taxonomic discussion by Rho & Kim (2005). The first group includes species with elongate loop-shaped or elongate uni-spiral amphids in males — P. californicum Allen & Noffsinger, 1978 , P. floridense Allen & Noffsinger, 1978 , P. hopperi Allen & Noffsinger, 1978 , P. maggenti Decraemer, 1989 , P. meridionale (Kreis, 1937) , P. newelli Allen & Noffsinger, 1978 , P. singaporense Allen & Noffsinger, 1978 , and P. spinosum (Southern, 1914) . A second group includes species with doubled elongate spiral amphids in males - P. antarcticum Allen & Noffsinger, 1978 and P. jejuense Rho & Kim, 2005 .

Paradraconema pachylumbus sp. nov. belongs in the first group but clearly differs from all other species in posterior body shape in males: the cloacal region is remarkably enlarged towards the dorsal side. The conicocylindrical tail abruptly narrows due to the enlargement of cloacal region. The cloacal region of other species is cylindrical or somewhat swollen but not so peculiarly enlarged as in P. pachylumbus . Otherwise, P. pachylumbus sp. nov. is similar to P. f l o r i d e n s e, P. hopperi , P. singaporense and P. spinosum in having the annules longitudinally areolated on the swollen pharyngeal region (annules not longitudinally areolated in the other species). P. pachylumbus sp. nov. resembles P. floridense in having prominent eyespots (vs. obscure eyespots in D. singaporense ), a subventral pair of precloacal Acan-set (vs. single ventral Corn-set in P. h o p p e r i, no precloacal Acan-set nor Corn-set in P. s p i n o s u m) and the gubernaculum with thin lateral dilation (vs. without lateral dilation in the other species cf. Decraemer 1982). P. pachylumbus sp. nov. is distinguished from P. f l o r i d e n s e not only by the characteristics of male posterior body but by the number of setae on the tail region in males and females (8 setae on annulated region and 3 setae on non-annulated end vs. 3–6 and 1–2 for P. f l o r i d e n s e), the longer gubernaculum (25–27 μm vs. 10–19 μm in P. floridense ), and the shorter tail in males (3.4 abd long vs. 4.1–5.8 in P. floridense ).

Figures

FIGURE 2. Paradraconema pachylumbus sp. nov. Male (A – E, holotype ZIHU 4266): A) Entire body. B) Swollen pharyngeal region. C) Head. D) Posterior region. E) Spicule and Gubernaculum. Female (F, G, I, ZIHU 4268; H, ZIHU 4269): F) Entire body. G, H) Amphid. I) Posterior region. Left side view. Correct number of SvAT not illustrated. Scales: A, F, 50 µm; B, D, I, 20 µm; C, E, G, H, 10 µm.

Tables

TABLE 2. Morphometrics of Paradraconema pachylumbus sp. nov.

	ZIHU	ZIHU	ZIHU	ZIHU
Characters L a b	4266* 914 16.9 8.9	4267 895 14.0 8.4	4268 907 12.4 8.2	4269 968 12.3 8.3
c V(%) hcbd ph SER SER mbd	8.1 - 35 103 141 44	7.2 51.3 40 106 138 56	7.7 50.4 40 111 149 61	8.0 50.0 38 117 157 58
SERbd v	17 -	- 459	20 457	20 484