Litinium australis, Martelli, Antonela, Russo, Virginia Lo, Villares, Gabriela & Pastor De Ward, Catalina T., 2017

Martelli, Antonela, Russo, Virginia Lo, Villares, Gabriela & Pastor De Ward, Catalina T., 2017, Two new species of free-living marine nematodes of the family Oxystominidae Chitwood, 1935 (Enoplida) with a review of the genus Thalassoalaimus de Man, 1893 from the Argentine coast, Zootaxa 4250 (4), pp. 347-357 : 350-352

Litinium australis sp. n.

( Figures 2 & 4 (A–C); Table 1 )

Systematic position. Oxystominidae Chitwood, 1935 : Oxystomininae Chitwood, 1935 : Litinium Cobb, 1920

Type material. Holotype: adult male. Registration number CNP-NEM 1528; type locality: San José gulf; coordinates: 42°21’S, 64°08’W; sublittoral, mud sediments (59.8 m water depth). Collected by C.T. Pastor de Ward, 22 August 1984.

Paratype: adult female. Registration number CNP-NEM 1529. Same data as holotype.

Other material: One male and one juvenile. Registration number MACN-In 40898. Same data as holotype.

Etymology. In reference to the name of the sailboat, El Austral, with which the sample was collected.

Measurements. See Table 1 .

Description. Male (holotype): Cylindrical body, tapering slightly towards the anterior end (L = 2495 µm). Cuticle smooth. Somatic setae not seen. Buccal cavity small and narrow. Cephalic sensilla present in 6 + 6 + 4 circles. Six inner labial setae, 3.2 µm long, and six outer labial setae, 4 µm long. A crown of four cephalic setae (4 µm in length) at 2 c.d. from anterior end. Amphid and amphidial pouch conspicuous, situated 4 µm from anterior end. Amphidial fovea 6 µm wide and 9 µm long. Cephalic diameter 11 µm at level of amphid. Amphid width about 55% of the corresponding head diameter. Excretory pore located at 31 µm (3.9 c.d.) from anterior end.

Pharynx cylindrical (315 µm long), ending in a small weakly-developed bulb (18 µm in diameter). Body diameter at the base of pharynx 27 µm.

Reproductive system diorchic, testes opposed. Anterior and posterior testes situated to the left of the intestine. Spicules equal in length, 34 µm long, arcuate and cephalated (1.6 abd). Gubernaculum tubular, corpus 13 µm long, with apophysis, and capitulum 5 µm long. At least four precloacal organs observed, with one seta in each. The two closest to the cloaca are more conspicuous and the others are tiny. The first precloacal organ lies 32 µm anterior to the cloaca and has a seta 3 µm long. The other precloacal organs are 93 µm, 120 µm and 202 µm from the cloaca, each one with a 3 µm long seta. Tail short and round, 29 µm long, without caudal capsule.

Female (paratype): Female larger (L = 3455 µm) but similar to male in general body shape. One posterior ovary located on the right side of intestine, antidromously reflexed. Vulval orifice ventral, located at 20% of body length. Uterus and oviduct 2675 µm long and the antidromously reflexed ovary 200 µm in length. Vagina short and not thickened.

Differential diagnosis. Litinium australis sp. n. is characterized by the first and the second crown of setae of differing lengths, rounded tail, gubernaculum with apophysis, and by the presence of four precloacal papillae.

Litinium australis sp. n. resembles, in the similar shape and length of the tail (short and rounded): L. aequale , L. curticauda , L. obtusilobus , L. profundum , L. quangi , L. volutum and the recently-transferred species L. egregius , L. paramontemari , L. pirum and L. setosus . L. australis differs from L. aequale , L. curticauda , L. profundum , L.

quangi , L. egregius , L. paramontemari and L. setosus in the number of precloacal organs. L. pirum and L. volutum have as many precloacal organs as L. australis , which differs from these species, and from L. obtusilobus , in amphid shape and size and in length of the inner and outer labial setae.

Figures

FIGURE 2. Litinium australis sp. n.: (A) head region of holotype male (internal); (B) head region of holotype male (external); (C) posterior end of holotype male showing copulatory apparatus; (D) uterus view with vulva of paratype female; (E) head region of paratype female (external); (F) posterior end of paratype female. Scale bars: 20 µm.

FIGURE 4. Litinium australis sp. n.: (A) posterior end of holotype male showing copulatory apparatus; (B) general view of male; (C) head region of holotype male (external). Thalassoalaimus nestori sp. n.: (D) posterior end of holotype male showing copulatory apparatus; (E) general view of male; (F) head region of holotype male (external). Scale bars: 20 µm.

Tables

TABLE 1. Measurements (µm) of Litinium australis sp. n.

	Holotype	Paratype	Paratype	Paratype
	Male	Female	Male	Juvenile
n	-	1	1	1
L	2495.00	3455.00	2880.00	2935.00
a	95.96	90.92	102.86	97.83
b	7.92	8.97	6.62	7.62
c	86.03	107.97	99.31	91.72
Anterior cephalic setae, length	3.20	3.50	3.50	3.00
Posterior cephalic setae, length	4.00	3.50	4.50	3.50
Sub-cephalic setae, length	4.00	4.50	4.00	4.50
Cephalic diameter	8.00	8.50	8.50	8.00
Cs%	50.00	41.18	52.94	43.75
Amphid from anterior end	4.00	3.00	4.00	not seen
External amphid width	6.00	6.00	6.00	-
External amphid length	9.00	10.00	9.50	-
Bd at amphid level	11.00	10.00	11.00	-
Amph%	54.55	60.00	54.55	-
Nerve ring from anterior end	140.00	140.00	190.00	117.00
Oesophageal bulb diameter	18.00	31.20	28.00	23.00
Bd at oesophageal bulb level	27.50	37.00	34.50	29.00
Pharynx length	315.00	385.00	435.00	385.00
Maximum body diameter	26.00	38.00	28.00	30.00
Anterior end to anus, distance	2466.00	3423.00	2851.00	2903.00
Anal body diameter	21.00	28.00	23.00	25.00
Tail length	29.00	32.00	29.00	32.00
c’	1.38	1.14	1.14	1.28
Spicule length	34.00	-	29.00	-
Gubernaculum length	13.00	-	12.00	-
Vulva from anterior end	-	700.00	-	-
Vulva from anterior end/L (%)	-	20.26	-	-