Pseudosteineria anteramphida, Sun & Huang & Tang & Zang & Xiao & Tang, 2019

Sun, Yan, Huang, Yong, Tang, Hongshuo, Zang, Yu, Xiao, Hui & Tang, Xuexi, 2019, Two new free-living nematode species of the family Xyalidae from the Laizhou Bay of the Bohai Sea, China, Zootaxa 4614 (2), pp. 383-394 : 388-389

Pseudosteineria anteramphida sp. nov

( Figs. 3–4 )

Type material. Holotype: ♂ 1 on slide WF–21–1; Paratypes ♂ 2, ♂ 3, and ♀ 1, ♀ 2 on slides: WF–23–2; WF–37–1 and WF–37–2, respectively.

Type locality and habitat. Specimens were collected from intertidal silt sediment (0–2 cm surface layer) in the Laizhou Bay (37° 11′ 26″ N; 119° 10′ 52″ E) .

Etymology. The species name is derived from the Latin anter and the Greek amphid, meaning relatively anterior position of amphideal fovea in this species.

Measurements. All measurement data are given in Table 2 .

Description. Males. Body slender, gradually tapering towards both extremities. Cuticle striated, beginning at base of buccal cavity and ending at tail tip. Buccal cavity with hemispherical cheilostom and funnel-shaped pharyngostom. Labial region set off. Six lips slightly inflated. Six inner labial sensilla papilliform. Six outer labial sensilla setiform, strong and stout, 10 µm long. Four cephalic setae, 12–14 µm long, and arranged in one circle with the six outer labial sensilla. Very long subcephalic setae arranged densely in eight short longitudinal rows (subdorsal, laterodorsal, lateroventral and subventral on both sides of body) behind the amphideal fovea, 18 µm from the anterior end. Each group with 5–6 setae, and the length of these setae increasing gradually from anterior to posterior in every row. Length of shortest seta about 7 µm, longest one about 60 µm. Somatic setae short, scattered along the rest of body. Amphideal fovea large, circular, situated between cephalic setae and groups of long subcephalic setae, at a distance of 12 µm from anterior end. Pharynx cylindrical, 185–203 µm (about 20% of total body length). Pharyngo-intestinal junction with conical cardia. Nerve ring located at anterior portion of pharynx (i.e. 35% of pharyngeal length). Excretory-secretory system not observed. Tail conico-cylindrical, 140–146 µm (i.e. equal to 6.4–7.7 anal body diameters in length) long, with distal two fifths cylindrical. Tail tip bearing three terminal setae, up to 20 µm long. Three caudal glands within the tail. Reproductive system diorchic, testes opposed. Anterior testis outstretched and situated to left of intestine; posterior testis reflexed and situated to right of intestine. Both spicules slender, curved, cephalated proximally and tapered distally, equal to 1.8 anal body dimeters in length. Gubernaculum simple, tubular, encloses distal part of the spicule, without apophysis. Precloacal supplements absent. There is a precloacal seta on ventral body side, 10 µm long, 22 µm in front of cloaca.

Females. Similar to males in most respects except body slightly larger, subcephalic setae longer (the longest up to 80 µm) and amphideal fovea smaller. Reproductive system monodelphic, one anterior outstretched ovary, stretched forward to the base of pharynx, situated to left of intestine. Postvulaval uterine sac present. Oviduct a wide tube. Uterus a wide tube. Vagina straight. Vulva located at posterior portion of the body (i.e. 65% of the body length from the anterior end), opening via a small pore on ventral body side.

Differential diagnosis and discussion. Pseudosteineria anteramphida sp. nov. is characterized by having circular amphideal fovea situated between cephalic setae and the groups of long subcephalic setae, i.e. eight groups of long subcephalic setae are located posterior to amphideal fovea. Curved slender spicules with cephalated proximal end and tapered distal end, equal to 1.8 anal body diameters in length. Tubular gubernaculum without apophysis. No precloacal supplement. The species is very similar to P. ventropapillata Tchesunov, 2000 in the position of groups of long subcephalic setae, but differs from the latter in having shorter body (997–1183 µm vs. 1407–1449 µm), not jointed cephalic setae, no procloacal supplements (vs. 12–14 wart-shaped procloacal supplements) and lacking gubernacular apophysis (vs. presence of gubernacular apophysis). Moreover, the new species is similar to P. pavo and P. sagittispiculata in lacking the gubernacular apophysis. However, the new species differs from P. pavo in having shorter and slenderer male body (962–997 µm, a=25.3–34.4 vs. 1480 µm, a=16.3) and shorter spicules (33–34 µm vs. 56 µm), more posterior position of groups of long subcephalic setae (vs. at level with amphideal fovea). It differs from P. sagittispiculata in posterior position of groups of long subcephalic setae (posterior to amphideal fovea vs. at level with amphideal fovea), shorter cephalic setae (12–14 µm vs. 14-16 µm) and shape of spicules (L-shaped vs. sagittate). Further differences of Pseudosteineria anteramphida sp. nov. from the other species of the genus are specified in the key below.

Figures

FIGURE 3. Pseudosteineria anteramphida sp. nov. (A) anterior end of the male; (B) entire view of the female; (C) anterior end of the female; (D) posterior end of the male; (E) spicule and gubenaculum.

FIGURE 4. Pseudosteineria anteramphida sp. nov. (A) anterior end of the male; (B, C) head end of the female; (D) posterior end of the male; (E) cloacal region of the male. (Scales: A, B, C = 20 µm; D = 30 µm; E = 10 µm).