(Figures 1–3, Table 1)
Material examined. Type specimens. Holotype male, inventory slide no. Beibuwan 201137.
The habitat and locality. Beibu Gulf, the South China Sea. Collected on August 2011, 20 °39′N, 108°02′E, water depth 20 m, salinity 33.48‰; 20°38′N, 108°37′E, water depth 32 m, salinity 33.85‰; 20°39′N, 109°32′E, water depth 23 m, salinity 33.48‰; surface sediment layer (0–10 cm), muddy sediment. Male inventory slide no. Beibuwan 201101, 201112, 201115, 201165 and 201169. Female inventory slide no. Beibuwan 201102, 201128, 201133 and 201165.
Etymology. The name refers to the long spicules that characterize the new species.
Description. Male. Body long, slender, tapering toward both extremities. Cuticle with punctations from level of amphid to 2/3 of conical portion of tail. Lateral differentiation consisting of four longitudinal rows of larger dots in pharyngeal and tail regions, two rows of larger dots elsewhere. Somatic setae rare and sparse, 5 μm long. Head set-off by constriction posterior to cephalic setae. Six inner labial papillae, six outer labial setae. Four cephalic setae, equal to 0.4–0.8 corresponding body diameters long, outer labial setae slightly shorter. Amphideal fovea spiral, 3 turns, located immediately posterior to cephalic setae. Anterior portion of buccal cavity cup-shaped, posterior portion of buccal cavity cylindrical, cuticularized, with three strong cuticularized teeth at border to anterior portion. Pharynx widening slightly posteriorly, not forming true bulb. Nerve ring near middle of pharynx. Renette situated posterior to cardia; excretory pore situated posterior to nerve ring.
Reproductive system with two opposed and outstretched testes. Anterior testis to the left and posterior testis to the right of intestine. Spicules paired, equal to 3.2–3.8 cloacal body diameters in length, curved, proximal end strongly cephalated and tapering distally. Gubernaculum with two straight caudal apophyses. Twelve to sixteen tubular precloacal supplements present which are often difficult to distinguish. Tail slender, conico-cylindrical, posterior two thirds of tail conical with numerous short setae. Tail tip slightly enlarged, with three terminal setae. Three caudal glands and spinneret present.
Female. Similar to males but shorter. Reproductive system didelphic, amphidelphic, with outstretched ovaries; anterior ovary to the left of intestine and posterior ovary to the right of intestine. Vulva equatorial. Spermatheca present, often with numerous spermatozoa. Tail shorter than in males, conico-cylindrical, with several short caudal setae and three short terminal setae. Three caudal glands and spinneret present.
Diagnosis and relationships. Dorylaimopsis longispicula sp. n. is characterized by amphideal fovea with three turns, lateral differentiation consisting of four longitudinal rows of larger dots in pharyngeal and tail regions, two rows of larger dots in the middle regions; renette situated posterior to cardia; spicules 3.2–3.8 cloacal body diameters long and curved, twelve to sixteen tubular precloacal supplements present; tail tip with three terminal setae.
Dorylaimopsis longispicula sp. n. is morphologically similar to D. intermedia Gagarin, 2013, D. brevispiculata Gagarin, 2013, D. rabalaisi Zhang, 1992, D. gerardi Muthumbi et al., 1997, D. variabilis Muthumbi et al., 1997 and D. papilla Guo et al., 2018 in the pattern of lateral differentiation, namely three or four longitudinal rows on the pharyngeal and tail regions, two rows in the middle body portion and with simple arcuate spicules structure. Dorylaimopsis longispicula sp. n. differs from D. intermedia in the longer spicules (179–197 μm vs 149–164 μm in D. intermedia) and presence of precloacal supplements in males of new species. Dorylaimopsis longispicula sp. n. differs from D. rabalaisi in the numbers of amphidial fovea turns (3 vs 2.5–2.75 in D. rabalaisi), longer spicules (179–197 μm vs 60–97 μm in D. rabalaisi), and spicules cuticularisation without ventral discontinuity (“ventral opening”) near proximal end. In addition, D. longispicula sp. n. has much longer spicules than D. brevispiculata (179–197 μm vs 59–68 μm in D. brevispiculata), D. gerardi (3.2–3.8 vs 1.7–1.9 cloacal body diameter in D. gerardi) and D. variabilis (3.2–3.8 vs 1.8–2.4 cloacal body diameter in D. variabilis), and it can be distinguished from D. brevispiculata based on absence of precloacal supplements in D. brevispiculata, and differs from D. variabilis and D. papilla by spicules with capitulum in D. variabilis and D. papilla.