Free-living nematodes of the genus Syringolaimus de Man, 1888 (Nematoda, Enoplida, Ironidae) from the Angola Basin, South-East Atlantic Abyss Author Tchesunov, Alexei V. text Zootaxa 2017 4306 4 478 500 journal article 32368 10.11646/zootaxa.4306.4.2 fb6de4a9-e368-4d18-9251-94cf4d0891fe 1175-5326 845097 D0481032-B34B-4114-85DA-7B8CD20371F6 Syringolaimus smolae Lima , Lins, Da Silva & Esteves, 2009 ( Figures 4–6 , Table 3 ) Material. Ten males and four females from both stations 325 (st. 325/4 Muc 8, 325/7 Muc8) and 346 (st. 346/1 Muc 3, 346/2 Muc 3). Description. Body slim and graceful. Cuticle smooth and moderately thick, fine cross striations visible only on ventral side of cylindrical part of the tail. Anterior cuticle between apex and amphidial fovea forming a circular thickening. There are three equal cheilostomatal teeth just out from the mouth opening. All the teeth are double (split from base) and thus consist of two claw-like parts. The claws of each tooth are slightly unequal; in most specimens, dorsal tooth composed of larger left and smaller right claws, smaller and bigger claws in ventrosublateral pairs more variable in position. Length of teeth is 2.3–3.5 µm in males and 2.3–3.6 µm in females. Sensilla around the mouth opening not visible. Amphidial aperture a large transverse slit posterior to the cheilostomal teeth. Amphidial fovea as a pocket with a wisp of ciliary processes within. In males, width of the amphidial aperture is 4.2 µm or 29–45% of the corresponding body diameter, distance from the cephalic apex to the aperture is 13–18.4 µm; same figures in a female with discernible aperture are 4.2 µm, 35% and 16.6 µm, respectively. There are scarce and hardly visible tiny papillae along the body. Metanemes not visible. Pharyngostom a rather long tube, with sclerotized lumen but flexible. Pharynx slender and muscular throughout its length, with thick internal cuticular lining. Pharyngostom surrounded with narrow, non-muscular tissue. Posterior part of the pharynx enlarged in an oval bulb; its internal cuticular lining not modified but distinctly set off from the lining of the major part of the pharynx. Cardia external, shaped as a truncate cone. Anteriormost intestinal cells with homogeneous content different from other intestinal cells that make them similar to progaster of Monhysteridae . Intestine with internal glycocalyx layer partly detached. Tail consists of anterior conical and posterior cylindrical parts not sharply differentiated from one another. Tail curved dorsally in all male and female specimens. Tail end rounded, no indication of spinneret; however, one or more caudal gland cell bodies discernible in some specimens ( Fig. 6 A). Female reproductive system didelphic, amphidelphic; anterior ovary to the left, posterior ovary to the left of the intestine. Males monorchic, outstretched testis situated to the right or to the left and ventral of the intestine. Spermatozoa tadpole-like or drop-shaped, situated with knob-like nuclear part turned towards anterior end and tail-like part towards posterior end of the body, 13–16 µm long, transparent, with dense nucleus in the thick end. Vas deferens with granular walls, its anterior part narrowed, posterior part enlarged. Spicules weak and arcuate, broad, with truncate anterior end and knobbed posterior end. Gubernaculum small (8–12 µm), in a shape of a slightly curved bar. A small midventral supplementary organ is visible as a small mound with an internal canal situated just anterior (3.4–9.2 µm) to the cloacal opening. In some males, structures similar to sublateral precloacal and a postcloacal papillae are visible. Diagnosis. Body length 900–1190 µm, a=30–62. Tubular pharyngostom 39–60 µm long. Terminal pharyngeal bulb 28–40 µm long and 16–31 µm wide. Spicules 17–30 µm, weak and flexible. Precloacal supplementary papillum present. Tail cylindro-conical, with posterior cylindrical portion (47–80% of entire tail) always curved dorsally in both sexes; no terminal tube or spinneret. Discussion. The species fits well the description of S. smolae Lima et al ., 2009 in dimensions and shape of the tail but differs by: absence of visible secretory-excretory pore at the level of the nerve ring, absence of a terminal spinneret on the tail tip, rather broad and weak spicules versus ”setiform“ spicules mentioned for S. smolae . FIGURE 4. Syringolaimus smolae , entire bodies. A : male; B : female. Scale bars: A–B = 200 µ m. FIGURE 5. Syringolaimus smolae . A : head of a male; B : head of a female; C : pharyngeal region of a male. Scale bars: A–B = 20 µ m; C = 50 µ m. FIGURE 6. Syringolaimus smolae , tails. A: male; B: female. Scale bars: A–B = 20 µ m. TABLE 3. Morphometry of Syringolaimus smolae Lima et al ., 2009 from the Angola Basin abyss. Character Males (n=10) Females (n=4) Despite verbal statements about presence of the spinneret and setiform spicules in the text of the original diagnosis, the figures correspond well to respective organs of our specimens.

Bođy length, µ m	min)max 900)1190	mean 1068	stanđarđ đeviation 117	coefficient of variation 10.9	min)max 975)1039	mean 1008	stanđarđ đeviation 27.1	coefficient of variation 2.69
a	34.3)61.9	52.7	8.02	15.2	30.6)46.4	37.9	8.18	21.6
b	5.19)5.80	5.47	0.21	3.84	4.58)6.09	5.39	0.72	13.4
c	8.20)11.1	9.35	0.80	8.56	7.65)8.96	8.46	0.57	6.74
c'	5.29)8.62	6.67	1.10	16.5	5.61)6.92	6.44	0.57	8.85
V, %	)	)	)	)	55.4)62.6	59.1	3.27	5.53
Bođy điameter at the level of cephalic sensilla, µ m	7.20)13.0	10.4	2.02	19.4	8.70)14.3	10.6	2.64	25.0
Bođy điameter at the level of nerve ring, µ m	16.0)24.0	21.0	2.94	14.0	18.9)28.7	21.7	4.69	21.6
Bođy điameter at the level of carđia, µ m	18.0)33.0	22.9	4.20	18.4	20.0)36.0	24.7	7.58	30.7
Bođy điameter at the level of miđbođy, µ m	18.0)30.3	20.6	3.55	17.2	18.4)32.7	24.0	6.22	25.9
Bođy điameter at the level of anus/cloaca, µ m	15.3)24.0	18.5	2.41	13.0	17.0)23.7	18.8	3.28	17.4
Buccal cavity length, µ m	39.0)59.4	49.1	5.75	11.7	40.9)52.0	46.1	5.06	11.0
Length of terminal pharyngeal bulb, µ m	28.0)39.2	35.0	3.45	9.85	32.0)37.8	34.3	2.84	8.27
Wiđth of terminal pharyngeal bulb, µ m	16.0)30.0	20.2	4.06	20.1	16.5)30.9	21.0	6.65	31.6
Length of spicules along arc, µ m	16.9)30.0	23.4	4.08	17.4	)	)	)	)
Length of gubernaculum, µ m	8.00)11.8	9.78	1.65	16.9	)	)	)	)
Distal slenđer tail part as % of entire tail length	47.6)62.4	55.4	4.78	8.63	58.0)80.0	68.2	10.9	15.9

Gut content. Intestine may be empty or contain a sausage of medium-coarse-granular material with sparse light-refractive particles as well as spherical homogeneous and slightly heterogeneous drops.