Thalassoalaimus nestori, 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 : 352-355

Thalassoalaimus nestori sp. n.

( Figures 3 & 4 (D–F); Table 2 )

Systematic position. Oxystominidae Chitwood, 1935 : Oxystomininae Chitwood, 1935 : Thalassoalaimus de Man, 1893

Type material. Holotype: adult male. Registration number CNP-NEM 17149; type locality: “Banco Perdices” beach; coordinates: 40°47’S; 64°51’W; mid littoral, silty sediments. Collected by V. Lo Russo and G. Villares, 14 February 2009.

Paratype: adult female. Registration number CNP-NEM 17192. Same data as holotype.

Other material: Three males. Registration numbers CNP-NEM 18794, 18939 and 19142, locality: “Banco Perdices” beach; coordinates: 40°47’S; 64°51’W; high littoral, fine sand. Collected by V. Lo Russo and G. Villares, 14 February 2009.

One male, one female and two juveniles. Registration numbers CNP-NEM 17135, 17104, 17134 and 17253 respectively. Same data as holotype.

One juvenile. Registration number CNP-NEM 12977; locality: San Antonio city; coordinates: 40°43’S; 64°57’W; mid littoral, mid sand. Collected by V. Lo Russo and G. Villares, 13 February 2009.

Etymology. Dedicated to Néstor J. Cazzaniga in recognition of the help given during this project.

Measurements. See Table 2 .

Description. Male (holotype): Cylindrical body (L=2260 µm). Cuticle smooth. Somatic setae observed. Buccal cavity small and narrow. Cephalic sensilla present in 6 + 6 + 4 circles. Six inner and six outer labial setae 3 and 3.5 µm long, respectively. A crown of four cephalic setae (5 µm) at 3.5 c.d. from anterior end. Amphid and amphidial pouch conspicuous, situated at 1.5 µm from anterior end. Amphidial fovea 4 µm wide and 7 µm long. Amphid width about 61% of the corresponding head diameter. Excretory pore at 142 µm (23.7 c.d.) from anterior end.

Pharynx cylindrical (400 µm long), ending in a small poorly-developed bulb (12 µm in diameter). Body diameter at the base of pharynx 17 µm.

Reproductive system diorchic, testes opposed. Anterior and posterior testes situated to the left of the intestine. Spicules equal in length, 25 µm long, fusiform and with well-developed proximal cephalization. Gubernaculum 11 µm long, rounded at the proximal end. Two precloacal organs with a seta in each one. The first precloacal organ lies 37 µm anterior to the cloaca and has a seta 2 µm long and the second precloacal organ lies at 73 µm and has a seta 2 µm long. Tail conical, 51 µm long, with caudal capsule.

Female (paratype): Female similar to male in general body shape. Body 2325 µm long. One posterior ovary located on the right side of intestine, antidromously reflexed. Vulval orifice ventral, located at 35% of the body length. Uterus and oviduct are 350 µm long, with antidromously reflexed ovary 190 µm in length. Vagina short and conspicuous, walls not thickened.

Differential diagnosis. Thalassoalaimus nestori sp. n. is characterized by its short and equal cephalic setae, the length and position of the cervical setae, narrow body diameter and tail with conical shape.

T. nestori differs from T. brasiliensis in the length of cephalic setae and the shape of the tail (conical vs. rounded in T. brasiliensis ); T. septentrionalis by the length and position of cervical setae and the length and shape of gubernaculum; T. pacificus by the presence of gubernaculum, length of cephalic setae, and the number of precloacal organs; T. mediterraneus by the length of cephalic setae and the shape and length of the gubernaculum; and T. lissus by the length of the cervical setae, length and shape of gubernaculum and the distance from the cloaca to the first precloacal organ. T. nestori is closely related to T. macrosmaticus , with similar position and length of cephalic setae, but differs in body length and de Man’s ratios a, b and c (2260 µm, 132.9, 5.7 and 44.3 in T. nestori vs. 3290 µm, 96.1, 7.9 and 57.7 in the holotype of T. macrosmaticus ). These species also differ in the position of the precloacal organs, and length of the tail and gubernaculum.

Figures

FIGURE 3. Thalassoalaimus nestori 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 and ovary 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 2. Measurements (µm) of Thalassoalaimus nestori sp. n. including mean values (range).

	Holotype	Paratype	Paratypes	Other	Paratypes
	Male	Female	Males	Female	Juveniles
n	-	-	4	1	3
L	2260.00	2325.00	2205.00 (2050–2260)	2235.00	1498.67 (1135–1800)
a	132.94	86.11	123.17 (105.12–136.36)	111.75	86.20 (81.07–91.82)
b	5.65	5.81	6.54 (5.65–7.26)	5.81	5.12 (4.37–5.78)
c	44.31	40.79	50.96 (46.12–56.25)	42.98	36.87 (26.40–45.91)
Anterior cephalic setae, length	3.00	3.00	2.80 (2.50–3)	2.50	2.17 (2–2.50)
Posterior cephalic setae, length	3.50	3.00	3.13 (3–3.50)	3.00	2.83 (2.50–3)
Sub-cephalic setae, length	5.00	5.00	5.38 (5–6)	5.00	4.67 (4–5)
Cephalic diameter	6.00	6.50	5.63 (5–6)	6.50	5.17 (5–5.50)
Cs%	58.33	46.15	55.91 (50–63.64)	46.15	55.15 (45.45–60)
Amphid from anterior end	1.50	2.00	5.63 (5–6)	2.00	1.83 (1–2.50)
External amphid width	4.00	4.50	3.75 (3–4.50)	4.50	4.00 (3.50–4.50)
External amphid length	7.00	5.00	5.88 (5–7)	5.00	4.83 (4–6)
Bd at amphid level	6.50	7.00	6.63 (5–7.50)	7.00	6.17 (6–6.50)
Amph%	61.54	64.29	57.31 (446.67–69.23)	64.29	65.17 (53.85–75)
Nerve ring from anterior end	113.00	105.00	95.25 (85–108)	106.00	99 (87–120)
Oesophageal bulb diameter	12.00	14.00	11.75 (9–16)	13.50	14.83 (14–15.50)
Bd at oesophageal bulb level	17.00	20.00	17.28 (15.60–21)	18.50	18.17 (16.50–21)
Pharynx length	400.00	400.00	340 (310–400)	385.00	291.67 (260–345)
Maximum body diameter	17.00	27.00	18.13 (15.5–21.5)	20.00	17.33 (14–21)
Anterior end to anus, distance	2209.00	2268.00	2161.50 (2010–2215)	2183.00	1457.33 (1092–1753)
Anal body diameter	17.00	20.00	17.13 (14–22)	16.00	16.17 (13.50–19)
Tail length	51.00	57.00	43.50 (40–49)	52.00	41.33 (34–47)
c’	3.00	2.85	2.59 (2.05–2.88)	3.25	2.59 (2.13–3.19)
Spicule length	25.00	-	22.25 (21–24)	-	-
Gubernaculum length	11.00	-	10.50 (10–12)	-	-
Vulva from anterior end	-	825.00	-	760.00	-
Vulva from anterior end/L (%)	-	35.48	-	34.00	-