Litinium quangi Tchesunov, Nguyen Dinh Tu & Nguyen Vu Thanh

Tchesunov, Alexei V., Thanh, Nguyen Vu & Tu, Nguyen Dinh, 2014, A review of the genus Litinium Cobb, 1920 (Nematoda: Enoplida: Oxystominidae) with descriptions of four new species from two contrasting habitats, Zootaxa 3872 (1), pp. 57-74 : 60-64

Litinium quangi Tchesunov, Nguyen Dinh Tu & Nguyen Vu Thanh sp. n.

Figs 1 , 2 , Table 1

Material. Holotype male, three paratype males, allotype female and paratype female. All the specimens are deposited in the Vietnam National Museum of Nature (18 Hoang Quoc Viet, Caugiay , Hanoi, Vietnam) with slide numbers VNMN .0011 (holotype male, paratype male 3 and allotype female), VNMN .0012 (paratype male 1 and paratype female 1) and VNMN .0013 (paratype male 2).

Locality. South Vietnam coast, Dong Nai River Delta, Can Gio National Reserve , 10°32'176''N and 106°45'919''E, 0.5 m deep . Sediment consisted of silt and clay (80.5%) and sand (19.5%). NaCl content 13.5‰.

Description. Body very long and slender, filiform. Cuticle thick, smooth over entire body. Head slightly separated off by a very slight narrowing at the level of the cephalic setae. Cuticle anterior to the amphideal fovea 1–1.3 µ m thick, posterior to the amphideal fovea 1.6–2 µ m, posterior to the cardia 2–3.4 µ m, tail terminal cuticle 3.9–4.2 µ m.

Six inner labial and six outer labial sensilla equal in length and shape. Both circles united in a joint crown of twelve short setae where outer labial setae situated just posterior to inner labial setae. Four equally short cephalic setae situated separately just posterior to the amphideal foveas in area of postcephalic narrowing.

Amphideal fovea large, longitudinally ovoid, with distinct cuticularised horseshoe-shaped fringe; aperture round, with very fine rim, located at anterior end of fovea.

A few short ventral, subventral and lateral papillae and tiny setae situated posterior to the amphideal fovea, anterior to the excretory pore, at 62–67 µ m from anterior end. A very minute midventral seta about 1 Μ m long present 10–12 Μ m anterior to the ventral pore.

No metanemes found.

Mouth opening tiny. Buccal cavity not developed as such and its walls not differentiated from the cuticular lining of the pharynx. Pharynx evenly muscular and slender throughout its length but widening gradually to the posterior end. Cardia widely conical and surrounded by intestinal tissue. Midgut lumen is partially filled with mass of fine granular material.

Ventral pore at about half distance from anterior end to the nerve ring, and posterior to the midventral seta. Only anterior portion of ventral gland duct discernible.

Vulva situated at ~ one fifth of body length from anterior end. Single posterior antidromously reflected ovary disposed ventrally and slightly to the left of the intestine. Uterus elongate and voluminous; uterus empty in both females examined. A short spermatheca just posterior to the uterus filled densely with minute round spermatozoa.

Only anterior male gonad present, situated ventrally to the intestine.

Spicules short, flat, arcuate, with internal cuticular linear longitudinal stripes, with posterior ends pointed and anterior ends slightly narrowed. One short (0.8–2, µ m long) midventral precloacal seta present, just anterior to the anterior ends of the spicules, 32–35 µ m from the cloacal opening.

Tail very short, rounded. Terminal pore and canal well developed, slightly subterminal. A pair of short subventral seta mid-tail length in both males and females; one ventral papilloid sensilla situated at mid-tail length discernible in some specimens.

Diagnosis. Litinium . Body length 2523–2918 µ m; a 81–118; c 72.1–97.2; c' 1.12–1.63. Inner labial, outer labial, cephalic setae very short, 1.4–2.6 µ m. Amphideal fovea ovoid in outline, with horseshoe-shaped cuticular rim. Cephalic setae at level of posterior end of the amphideal fovea. One precloacal midventral supplementary seta at level of anterior endof the spicules.

Character Specimens Differential diagnosis. Litinium quangi sp. n. shares the ovoid shape of the amphideal fovea having a small round aperture with L. aequale , L. curticauda , L. parmatum , L. subterraneum and Litinium sp. 1 of Quang et al. (2008) but other known species have a fovea shaped as a half moon. Litinium quangi differs from all species by having only one midventral preanal seta instead of two or more setae. The female of L. quangi differs from L. parmatum with unknown males by having smaller anterior sensilla (1.1–2.5 vs 18 µ m) and a shorter rounded tail (c' 1.12 vs 4.2, conical tail). Litinium quangi differs from the most similar and sympatric species L. sp. 1 of Quang et al. (2008) by having shorter outer labial and cephalic setae (respectively, 2.1–2.6 µ m and 1.4–2.2 µ m vs 5.2 µ m and 4.4 µ m) and one vs two midventral precloacal setae. Litinium guangi differs from L. curticauda in the number of precloacal supplementary setae and by the greater distance from the head apex to the ventral pore (68–75 µ m vs 39.5–48 µ m), shorter spicules (30–33 µ m vs 43–49 µ m), slightly longer tail (c 72.1–94.1 and c ' 1.36–1.63 vs 110–119 and 0.83–0.94, respectively).

Etymology. Species name is given in honour of Dr. Quang Ngo Xuan, the first author of the paper describing several Oxystominidae species from the Can Gio mangrove forest where two unnamed Litinium species were collected.

Figures

FIGURE 1. Litinium quangi sp. n., entire and anterior body. A: holotype male, entire; B: allotype female, entire; C: holotype male, anterior body; D: allotype female, anterior body. Scale bars: A, B 500 µ m; C, D 100 µ m.

FIGURE 2. Litinium quangi sp. n., anteriors and tails. A: holotype male, anterior body end; B: allotype female, anterior body end; C: holotype male, posterior body end; D: allotype female, tail. Scale bars: 20 µ m.

Tables

TABLE 1. Morphometry of Litinium quangi sp. n. Measurements in µ m.

	Holotype male	Paratype male Paratype male Paratype male 3 Allotype 1 2 female	Paratype female 1
L a b	2523 109 9.59	2762 2726 2918 2877 103 115 118 83.6 9.18 9.37 10.8 10.3	2696 81.2 11
c V, % c'	72.1 - 1.63	81.2 89.4 94.1 97.2 - - - 18.7 1.49 1.36 1.47 1.12	? 18.5?
diam.c.s. diam.am. diam.n.r.	8.4 12.4 21.7	9.1 7.8 8 7.6 9.9 9.5 11.8 11.4 22.7 26.3 23.4 24	9 11 23.6
diam.ca. diam.midb. diam.ani	26 23.2 21.5	31.2 33.8 27.9 30 26.8 23.7 24.7 34.4 23 22.5 21.1 26.4	32 33.2 27.8
i.l.s. o.l.s. c.s.	2 2.6 2.2	2.2 2 2.1 1.5 2.1 2.1 2.2 1.5 2 1.9 1.4 2.5	1.4 1.5 2.4
dis.c.s. dis.am. am.l.	15.6 2.9 11	19? 15? 4.3 4.5 3.6 3.8 8.1 8.7 11.1 9.8	? 3.2 9.3
am.w. dis. v.pore spic.arc	8.1 75 30.4	?? 7.4 6.8? 68 72.7 80.5 30.4 32.9 33.1 -	?? -