Diplopeltoides nudus Tchesunov 2006

Diplopeltoides nudus (Gerlach, 1956)

Fig. 7; Table 4

Diagnosis

Diplopeltoides nudus is characterised by by a body of 0.94–1.35 mm long; cuticle without longitudinal striation; cuticularised plate absent; cephalic sensilla papilliform, 1–1.5 µm long; amphidial fovea an inverted U-shape, 17–28 µm long and 6–8 µm wide; narrow space between amphidial branches with crenated edge; secretory-excretory pore located opposite to basal pharyngeal swelling; tail subcylindrical with bluntly rounded terminus; testes outstretched; spicules 29–38 µm long, strongly curved, with dorsally bent manubrium and subcylindrical, gradually narrowing shaft; gubernaculum plate-like, with or without caudal apophyses.

Material examined

SWEDEN: 2 ♀♀, 1 ♂, Skagerrak, 58°23′00.8″–22′00.8″ N, 10°20′28.8″–38.3″ E, soft bottom 390– 428 m deep, 10 Oct. 2012, “Inventering Bratten” leg. (SMNH-159566); 2 ♂♂, Skagerrak, 58°22′17.8″– 19.4″ N, 10°23′50.8″–24′03.2″ E, soft bottom 351–387 m deep, 10 Oct. 2012, “Inventering Bratten” leg. (SMNH-159567).

Description

Adult

Body cylindrical, posteriorly tapering in the tail region, straight or curved upon fixation. Cuticle coarsely annulated along entire body, except for smooth anterior end and terminal part of tail; annules 2–2.5 µm wide at mid-body region; longitudinal striation not observed under light microscope. Somatic setae present on tail. Labial region bluntly rounded. Cuticularised plate underlying cephalic cuticle around amphid absent. Inner and outer labial sensilla not seen. Cephalic sensilla papilliform, equal to 0.1 labial region diameter in length, their bases are located 3.5–4 µm from anterior end. Amphids similar in shape and size between sexes: amphidial fovea an inverted U-shape with dorsal branch longer than ventral branch. Narrow space between amphidial branches (amphidial shield) cuticularised with crenated edge. Stoma very small, its cuticularised lining uniform with lining of the pharynx. Pharynx distinctly subdivided into anterior corpus and posterior postcorpus; corpus cylindrical or slightly fusiform, muscular; postcorpus consists of anterior narrow non-muscular isthmus and pear-shaped glandular basal swelling. Pharyngeal gland nuclei and orifices indistinct. Nerve ring surrounding isthmus. Secretoryexcretory system present; secretory-excretory pore located along ventral body line opposite to basal pharyngeal swelling; secretory-excretory duct very short, leading from pore to ampulla; renette cell obscure. Tail subcylindrical with bluntly rounded terminus. Caudal glands opening via three separate openings, spinneret absent.

Female

Reproductive system didelphic, amphidelphic, reflexed; ovary branches symmetrical. Anterior ovary situated to either right or left of intestine; posterior ovary situated to left of intestine. Vulva located immediately posterior to mid-body. Vagina straight, 0.3 of vulval body diameter, with thick walls and

developed sphincter muscle at its proximal part; pars refringens vaginae absent. Intrauterine egg not seen; sperm is visible in the uterus. Rectum short, 0.6–0.9 of the corresponding body diameter long.

Male

Reproductive system diorchic, both testes outstretched. Spicules paired and symmetrical, strongly curved, with dorsally bent manubrium and subcylindrical, gradually narrowing shaft. Gubernaculum plate-like, with a pair of strong closely set caudal apophyses. Caudal setae present, arranged in subventral and subdorsal rows but difficult to observe and count.

Remarks

The recently collected population of D. nudus is similar to the type specimens in general morphology and measurements, including the characteristic spicule shape, except for the somewhat longer spicules (35–38 µm vs 29 µm in type specimens) and the presence of gubernaculum apophyses (vs absent in type specimens). As noted in the redescription of D. bulbosus, gubernaculum apophyses may be indistinct or absent in some specimens and should not be used as the sole diagnostic character.