Enoplolaimus lenunculus Wieser, 1959

Meng, Zhiyu, Liang, Huixin & Wang, Chunming, 2025, Phylogenetic analysis within Monhysteridae and Thoracostomopsidae based on rDNA sequences and two new species from the Yellow Sea, China, Zoosystematics and Evolution 101 (3), pp. 1339-1358 : 1339-1358

Description of Enoplolaimus lenunculus Wieser, 1959

Figs 6 , 7 , 8 , Table 5

Materials examined.

Four males and three females were collected from Station TJGK in October 2023. ♂ 1 on slide number 23 TJGK-Q-3-1-5 ; m # 2, m # 3, and f # 3 on 23 TJGK-Q-3-1-3 ; f # 1 and f # 2 on TJGK-Q-3-1-6 .

Collection locality and habitat.

All specimens were collected from Changdao Island, Shandong Province, China. 38°9'N, 120°44'E ( TJGK), 0–2 cm sediment depth, sandy sediment.

Measurement.

All measurement data can be found in Table 5 .

Description.

Male. Body long, cylindrical, slightly tapered posteriorly. Cuticle smooth. Head dome-shaped and set off with three lips, without striations. Each lip carrying a triangular lip lobe and separated by clefts, bearing two inner labial sensilla. Cephalic organ oval-shaped, just posterior to inner labial setae. Six inner labial setae long, 0.39–0.51 head diameter in length. Six outer labial setae and four cephalic setae in one circle, positioned at level of posterior margin of cephalic capsule. Rows of 8 subcephalic setae situated behind the cephalic sensilla, 15–17 µm in length. Cephalic capsule well developed. Buccal cavity conical with three equal-sized mandibles and three onchia. Mandibles well developed, each consisting of two lateral rods and one curved bar. Three onchia, one dorsal large and two ventrosublateral small. Amphidial fovea and excretory pore not observed. Pharynx cylindrical.

Male reproductive system diorchic, anterior and posterior testes outstretched. Spicules arcuated and symmetrical, 1.3–1.7 cloacal body diameters in length. Gubernaculum short. Precloacal supplement tubular-shaped, 8 µm in length, 72–82 µm from cloacal. Tail conico-cylindrical with terminal setae, 2.8–3.4 cloacal body diameters in length. Three caudal glands with a common duct.

Female. Similar to male in general body shape. Reproductive system didelphic and amphidelphic, ovaries reflexed. Vagina with thick walls. Sphincter muscles well developed, present at oviduct and posterior ovary. Vulva located at slightly posterior portion of the body (57–62 % of the body length from the anterior end).

Remarks.

The Changdao specimens are largely consistent with the description of E. lenunculus by Wieser (1959) based on specimens from Bainbridge Island. However, the following discrepancies were observed between specimens from Changdao and the Bainbridge Island: subcephalic setae (absent in original description), cephalic setae length (16–23 µm vs. 12 µm), tail length (2.8–3.2 a. b. d. vs. 3.3–3.5 a. b. d.), and supplement distance from cloacal (72–82 µm vs. 90 µm).

Figures

Figure 6. Enoplolaimus lenunculus. A. Lateral view of the male anterior region; B. Lateral view of the male anterior region showing buccal cavity, onchia, and mandibles; C. Lateral view of the female anterior region; D. Lateral view of the male posterior body; E. Spicules and gubernaculum; F. Lateral view of the female posterior body showing the tail region. Scale bars: 50 µm (A, C, F); 30 µm (B, D); 20 µm (E).

Figure 7. Enoplolaimus lenunculus A. Lateral view of the female entire body; B. Lateral view of the male entire body. Scale bars: 100 µm.

Figure 8. Enoplolaimus lenunculus. A. Lateral view of the male anterior region; B. Lateral view of the male anterior region showing mandibles; C. Lateral view of the male posterior body, showing precloacal supplement; D. Lateral view of the male posterior region showing spicules; E. Lateral view of the male posterior body, showing gubernaculum; F. Lateral view of the female posterior body, showing sphincter muscles (arrow). Scale bars: 20 µm (A – F).