Ethmolaimus multispiralis, Ban & Li & Huang, 2024

Ban, Shuyan, Li, Ting & Huang, Yong, 2024, A new species of the genus Ethmolaimus de Man, 1880 (Nematoda, Ethmolaimidae) from intertidal zone of the Yellow Sea, China, Zoological Systematics 49 (2), pp. 175-180 : 175-180

Ethmolaimus multispiralis sp. nov. ( Figs 1–3 )

Diagnosis. The species is characterized by: amphidial fovea multispiral with 2.5 turns in male and 1.5 turns in female; cephalic sensilla setiform in male and papilliform in female; pharynx with a posterior oblong bulb; spicules slightly curved, cephalated proximally and pointed distally; lateral piece present with bent distal end; gubernaculum as a slender rod; two small alveole-like and 12–14 cup-shaped precloacal supplements in front of cloaca; tail conical with a short posterior cylindrical portion.

Description. Male. Body spindle, tapering towards both ends. Cuticle with transverse rows of even dots, without lateral differentiation. Inner labial sensilla indistinct. Six outer labial sensilla papilliform, 1.5µm long. Four cephalic setae 4–5 µm long. Somatic setae not observed. Amphidial fovea multispiral with 2.5 turns, 5–7 µm in diameter with anterior border 10– 12 µm from anterior end. Buccal cavity consisting of two portions: anterior one cup-shaped with weakly sclerotized walls; posterior one cylindrical with sclerotized walls, 20–25 µm in depth. One dorsal tooth and two subventral teeth inserted at junction between two portions, of which dorsal one larger and more sclerotized than subventral teeth. Pharynx surrounding buccal cavity anteriorly, its posterior portion enlarged to an oblong bulb. Cardia small. Nerve ring located at 59% of pharyngeal length from anterior end. Ventral gland cell behind cardia and opening through a pore just anterior to posterior pharyngeal bulb. Tail conical with posterior third cylindrical portion, 3.1–3.7 times cloacal body diameters long. Three caudal gland cells present. Spinneret distinct.

Reproductive system apparently monorchid, with an anterior outstretched testis, situated left side of intestine, about 290 µm long. Spicules slender, slightly curved, cephalate proximally and narrowed gradually to pointed distally, 1.8–2.0 times cloacal body diameters long; lateral piece (telamon) present with bent distal end; gubernaculum as a slender rod, 15– 21 µm long. Two small alveole-like and 12–14 cup-shaped precloacal supplements in front of cloaca. Cuticle strongly annulated cuticularized between cup-shaped supplements, apparently with cuticle ridges between supplements. Anteriormost supplement 225–257 µm from cloaca; posteriormost one 17–21 µm from cloaca; two alveolar supplements close to cloaca.

Female. Similar to males in morphological features except cephalic sensilla papilliform, amphidial fovea with 1.5 turns, tail slightly longer. Reproductive system didelphic with two opposite and reflexed ovaries; both gonads on different sides of intestine. Vulva located at about 50–53% of body length from anterior end. Spermatheca present.

Juvenile. Similar to female, except body slender and amphids smaller, 3 µm in diameter.

Measurements see Table 1.

Material examined. Holotype ♂ (slide no. RZLS 2021-2-8 -37), the surface layer of the silt beach at an intertidal zone along the Rizhao coast, Rizhao, Shandong, China (35°5′11″N, 119°19′39″E), II.2021, coll. Yingdong Hao. Paratypes. 1♂, 2 juveniles, same data as holotype; 1♂ 2♀ (slide no. YMD 2022-1-2-7), 1♂ (slide no. YMD 2022-2-2-14), the surface layer of the mud flat at the intertidal area of Yangmadao coast, Yantai, Shandong, China (37°26′1″N, 121°36′37″E), I.2022, coll. Shuyan Ban.

Etymology. The species name is from Latin adjective multi and spiralis, referring to the species with multispiral amphid.

Discussion. The new species is similar to E. multipapillatus Paramonov, 1926 by having multispiral amphidial fovea, but differs from the latter by the cephalic sensilla setiform in male (vs. papilliform in E. multipapillatus ), tail conico-cylindrical (vs. conical), males with two small alveole-like and 12–14 cup-shaped precloacal supplements, without seta in front of the cloaca, while the latter species having 17–24 cup-shaped precloacal supplements and a single seta in front of the cloaca. The new species differs from other species within the genus mainly by multispiral amphidial fovea, both alveole-like and cup-shaped precloacal supplements.

Key to the marine species of Ethmolaimus (based on Jensen, 1994).

1. Amphid posterior to buccal cavity, body shorter than 500 µm ..................................................................................... E. hailuotoensis

Amphid at level with buccal cavity region, body longer than 500 µm ................................................................................................. 2 2. Amphid multispiral with two or more turns at least in male ................................................................................................................ 3

Amphid unispiral with single turn........................................................................................................................................................ 4 3. Cephalic sensilla papilliform, tail conical, males with 17–24 cup-shaped precloacal supplements .......................... E. multipapillatus

Cephalic sensilla setiform, tail conico-cylindrical, males with 12–14 cup-shaped precloacal supplements.... E. multispiralis sp. nov. 4. Body with extremely long somatic setae, longer than 200 µm ............................................................................................. E. hirsutus

Somatic setae little and short................................................................................................................................................................5 5. Outer labial sensilla papilliform ...........................................................................................................................................................6

Outer labial sensilla setiform................................................................................................................................................................ 7 6. Spicules slender and sickle-shaped, amphid situated middle of buccal cavity .................................................................. E. bothnicus

Spicules broad and not sickle-shaped, amphid situated base of buccal cavity ............................................................ E. parapratensis 7. Dorsal tooth much larger and subventral teeth transverse flanges, pharyngeal bulb spherical............................................. E. pratensi

Dorsal tooth slightly large, pharyngeal bulb slender ...................................................................................................... E. intermedius

Funding This work was supported by the National Natural Science Foundation of China (41676146). Acknowledgements We are very thankful to Ms Chunyan Qiao for her kind help in samples collection. We are sincerely grateful to two anonymous referees for reviewing and improving on the manuscript.

Shuyan Ban, Ting Li, Yong Huang *

College of Life Sciences, Liaocheng University, Liaocheng 252059, Shandong, China

* Corresponding author: E-mail: [e-mail]

Figures

Figure 1. Ethmolaimus multispiralis sp. nov. A. Anterior end of holotype, showing buccal cavity, teeth, cephalic setae, amphidial fovea and cuticle dots; B. Pharyngeal region of female, showing papilliform anterior sensilla, amphid, pharyngeal bulb and excretory system; C. Entire body of holotype; D. Cloacal region of holotype, showing spicule, lateral piece, gubernaculum and precloacal supplement; E. Entire body of female. Scale bars:A, B, D=20 µm. C, E=50µm.

Figure 2. Ethmolaimus multispiralis sp. nov. A.Anterior end of holotype, showing buccal cavity, teeth, outer labial and cephalic setae; B. Anterior end of male, showing amphidial fovea and cuticle dots; C. Amphidial fovea of male; D. Pharyngeal bulb; E. Posterior portion of holotype, showing spicule and precloacal supplement; F. Cloacal region of holotype, showing spicule, lateral piece, gubernaculum and precloacal supplement. Scale bars: A–C =10 µm; D–F =20µm.

Figure 3. Ethmolaimus multispiralis sp. nov. A. Lateral view of entire female; B. Anterior end of female, showing amphidial fovea (arrow) and cuticle punctation; C. Pharyngeal region of female, showing buccal cavity, anterior and posterior pharyngeal bulbs, and excretory system (arrows). Scale bars: A =50µm; B=10 µm; C=20µm.