Sabatieria parvamphis Yang & Guo & Chen & Lin 2019, sp. n.

Sabatieria parvamphis sp. n.

(Figures 5–7, Tables 1, 3)

Type material. Five males and two females were collected from station CC 1.

Holotype: ♂ 1 on slide number Chukchi20100720 CC14206. Paratypes: ♂ 2 on slide number Chukchi20100720 CC14206, ♂ 3 on Chukchi20100720 CC14203, ♂ 4 on Chukchi20100720 CC14210, ♂ 5 on Chukchi20100720 CC14211, ♀ 1 on Chukchi20100720 CC14212, ♀ 2 on Chukchi20100720 CC12207.

Type locality and habitat. All specimens were collected from the Chukchi Sea (52 m water depth). Station CC 1: 67.6722°N, 168.9562°W. Median grain diameter: 5.35 Md Φ, Sand: 33.34%, Silt: 58.02%, Clay: 8.63%.

Etymology. The species name is derived from the latin parvus (=small) and amphis (=amphid), and refers to the small amphid in this species relative to other species of the ornata group.

Measurements. Table 1.

Description. Male. Body cylindrical, tapering slightly towards both extremities. Cuticle with transverse rows of dots, lateral differentiation consisting of larger, irregularly-spaced dots. Two dorso- and two ventro-lateral rows of short, sparse somatic setae. Three crowns of anterior sensilla: six inner labial papillae, six short but distinct outer labial setae and four short cephalic setae. Buccal cavity cup-shaped. Amphideal fovea spiral with 3.25 turns, located immediately posterior to cephalic setae. Pharynx gradually swelling towards posterior, not forming true bulb. Nerve ring 143–157 µm from anterior end of body, at 52–57% of the pharyngeal region length. Excretory pore 161–193 µm from anterior end of body, at 59–66% of the pharyngeal region length. Tail 197–209 µm long, conico-cylindrical with four rows of sparse short caudal setae and three short terminal setae. Reproductive system diorchic, with outstretched testes. Anterior testis to the left of intestine, posterior testis to the right of intestine. Spicules paired, equal, arcuate, equal to 1.2–1.4 cloacal body diameters in length. Gubernaculum with 28–32 µm long, with paired, curved apophyses. Thirteen to fifteen prominent tubular pre-cloacal supplements with distance between adjacent supplements increasing towards anterior, followed by one pre-cloacal seta. Three caudal glands situated posterior to spicule. Spinneret present.

Female. Similar to male, except for longer total body length and longer tail length. Reproductive system didelphic, ovaries opposed, outstretched, with anterior branch to the left of intestine and posterior branch to the right of intestine. Mature eggs are oval-shaped. Spermatheca not observed. Vulva located at 46–49% of the body length. Vaginal glands not observed, pars proximalis vaginae surrounded by constrictor muscle. Three caudal glands situated posterior to anus. Spinneret present.

Diagnosis and relationships. Sabatieria parvamphis sp. n. is characterized by short cephalic setae (6–7 µm, equal to 31–38% of head diameter), small amphideal fovea (equal to 55–72% corresponding body diameter), amphideal fovea spiral with 3.25 turns, curved gubernacular apophyses, thirteen to fifteen prominent tubular precloacal supplements with distance between adjacent supplements increasing towards the anterior, tail length equal to 3.5–4.8 cloacal body diameters.

Sabatieria parvamphis sp. n. belongs to the ornata group based on the presence of curved gubernacular apophyses, and pre-cloacal supplements with distance between adjacent supplements increasing towards the anterior. There are five valid species in this group now. S. parvamphis sp. n. can be differentiated from all other species of the group by relatively small amphideal fovea (equal to 55–72% corresponding body diameter) and short cephalic setae (6–7 µm, equal to 31–38% of head diameter). Besides, S. parvamphis sp. n. can be differentiated from S. macramphis and S. longisetosa by the length of cephalic setae (equal to 31–38% vs 140–170%; 100% head diameter, respectively). S. parvamphis sp. n. can be differentiated from S. abyssalis in the number of pre-cloacal supplements (13–15 vs 10). S. parvamphis sp. n. and S. stenocephalus can be distinguished according to body shape – in S. stenocephalus anterior part of the body is very sharp-pointed (Huang & Zhang, 2006). S. parvamphis sp. n. resembles S. ornata in the number of pre-cloacal supplements and tail shape, but differs from it in longer total body length (2180–2730 vs 1350–2240 µm) and shorter tail (c’=3.5–4.0 vs 3.8–4.6).