Terschellingia longicaudata de Man, 1907

Hong, Jung-Ho, Kim, Kichoon & Lee, Seunghan Lee and Kanghyun, 2024, Four unrecorded species of free-living nematodes from the sublittoral zone in the East Sea, Korea, Journal of Species Research 13 (2), pp. 147-158 : 153

Terschellingia longicaudata de Man, 1907

( Fig. 3 , Table 3)

Locality. The specimens were collected from the subtidal middle part of the East Sea, Korea, specifically along the coast of Yangyang (38°4 ʹ 50.2 ʺ N, 128°42 ʹ 32.9 ʺ E). The collection site was located at a depth of 68m in clay sediment .

Material. Four males ( MABIK NA00157786 , MABIK NA00158070 - MABIK NA00158072 ) and two females ( MABIK NA00158073 - MABIK NA00158074 ) were collected by Seunghan Lee on the coast of Yangyang on 6 May 2022, aboard the Research Vessel Haeyanghwnangkyung 3 .

Measurements. See Table 3 for detailed measurements and morphometric ratios.

Description. Males ( Fig. 3 , Table 3). Body slender, long and fusiform with long conical-cylindrical tail. Cuticle smooth and finely striated. Head rounded slightly truncate at anterior end. Six inner, labial papillae. Six cephalic setae 4-5 μm long. Four subcephalic setae 4-5 μm long, forming a circle at amphids level (12-13 μm from anterior end). Amphidial fovea circular and sclerotized, 7.5- 8.5 μm in diameter (about 0.5 cbd), situated at 4 μm from anterior end. Small buccal cavity shallow cup-shaped and unsclerotized. Pharynx cylindrical with an elongated and slightly expanded posterior potion, muscular, posteriorly forming a well-pronounced bulb(24-25 μm wide). Cardia conical (21-24 μm long), projecting into intestine. Nerve ring 69-85 μm behind anterior end or 43% of pharyngeal length. Ventral gland located at junction of pharynx and intestine. Excretory pore just located below nerve ring, 72-88 μm from anterior end. Tail elongates, about 12.2- 16.6 a.b.d., conical with a long filiform portion constituting about over 80% of total tail length (255-402 μm long). Testes outstretched; reflexed posterior are similar in length. Both testis to left of intestine. Long and thin vas deferens well-developed. Spicules paired, slender and arcuate, 1.4-1.5 a.b.d. long as curve, cephalate and ventrally bent proximally. Gubernaculum with a pair of 10- 12 μm dorsal caudal apophysis. One precloacal seta, 2-3 μm long. Precloacal supplement absent.

Females ( Fig. 3 , Table 3). Similar to male. Reproductive system didelphic, with two outstretched ovaries. Vulva with slightly raised lips, situated at pre-median of body (41.4-43.2% of body length).

Remarks. Terschellingia longicaudata de Man, 1907 is characterized by the absence of teeth in the buccal cavity, the amphidial fovea positioned near the anterior end, setiform cephalic setae, subcephalic setae at the level of the amphids, the formation of a well-pronounced bulb in the pharynx, a long cylindrical portion of the tail (over 50%), spicule ratio (s) lower than 1.7, gubernaculum with apophysis, and the presence of a posterior ovary ( Armenteros et al., 2009). The specimens from the East Sea, Korea, generally conform to the original description by de Man(1907), except for the ‘de Man ratio a,’ which was higher in the type specimens (a= 43-46 vs. 20-28). Additionally, there are slight differences in body width (30-38 μm vs. 40-62 μm) and spicule length ratio (s = 1.4-1.5 vs. 0.9-1.0). We interpret this variation as intraspecific diversity.

Figures

Fig. 3. Terschellingia longicaudata de Man, 1907, from the East Sea, Korea.A, Male pharynx; B, Male copulatory apparatus; C, Male habitus; D, female vulva. Scale bars: 20μm (A, B) and 100μm (C, D).