Setoplectus minor, Lu & Sui & Huang, 2022

Lu, Yang, Sui, Xinxin & Huang, Yong, 2022, Three new species of free-living marine nematodes from the central basin of the South China Sea, Journal of Natural History 56 (17 - 20), pp. 1091-1107 : 1103

Setoplectus minor sp. nov.

( Figures 5–6 and Table 2 )

Type material

One male and one female were found and measured. Holotype male on slide NHS74-279-1, paratype female on slide NHS79-289-7.

Type locality and habitat

Holotype was found in muddy clay sediment at Station S 74 in the South China Sea (10.013° N, 115.147°E, water depth 1951 m) . Paratype female was found in muddy clay sediment at Station S 79 in the South China Sea (10.751°N, 114.983°E, water depth 2390 m).

Etymology

The species name is derived from the Latin adjective minor (minute), referring to its tiny body size relative to other members of the genus.

Measurements

All measurement data are given in Table 2 .

Description

Holotype male. Body elongate spindle, anterior third of pharyngeal region attenuated. Cuticle annulated, annules smooth. Inner and outer labial sensilla papilliform, located on the anterior surface of lips. Four cephalic setae each 2 µm long, located posteriorly to the labial region. Amphidial aperture circular, located at more posterior position of 5 times head diameters from the anterior end. Secretory–excretory system absent. Tubular buccal cavity long and narrow, occupying one-third of the total length of the pharynx. Pharynx guitar shaped, with a middle bulb and a basal bulb, with strongly developed cuticular lining. Mid-pharyngeal bulb rugby ball shaped and basal bulb pear shaped. Cardia cylindrical, partly enveloped by the intestinal tissue in its posterior part. Tail elongate conical with tapered terminus, without terminal setae, 4.3 times abd in length. Three caudal glands present. Spinneret functional.

Reproductive system diorchic. Spicules symmetrical, slightly arcuate, with cephalated proximal end and tapered distal end, 21 µm long. Gubernaculum rod-like, slightly curved, 8 µm long. A papilliform midventral precloacal supplement located at 9 µm in front of cloaca. Female. Similar to males in most morphological characteristics except amphidial aperture larger and oval in outline. Reproductive system didelphic with two opposed, outstretched ovaries. Spermatheca unseen. Vulva located at mid-body, 52% of body length from the anterior end. Vulval lips slightly raised. Vagina straight.

Figures

Figure 5. Setoplectus minor sp. nov. (a) Pharyngeal region of male, showing cephalic setae, amphid, and pharyngeal bulbs; (b) posterior region of male, showing spicule, gubernaculum and precloacal supplement; (c) anterior end of male, showing cephalic setae, buccal cavity and amphid; (d) entire female, showing amphid, pharyngeal bulb and reproductive system. Scale bars: a, b, c = 10 µm; d = 20 µm.

Figure 6. Setoplectus minor sp. nov. (a) Pharyngeal region of male, showing cephalic setae (arrow); (b) pharyngeal region of male, showing pharyngeal bulb and amphid (arrow); (c) cloacal region of male, showing spicule, gubernaculum and precloacal supplement; (d) entire female, showing amphid (arrow 1), pharyngeal bulb and valve (arrow 2). Scale bars: a, b, c = 10 µm; d = 20 µm.