Diplopeltoides nudus ( Gerlach, 1956 ), 2006

Holovachov, Oleksandr & Boström, Sven, 2017, Three new and five known species of Diplopeltoides Gerlach, 1962 (Nematoda, Diplopeltoididae) from Sweden, and a revision of the genus, European Journal of Taxonomy 369, pp. 1-35 : 17-20

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.

Figures

Fig. 7. Diplopeltoides nudus (Gerlach, 1956). A. Female pharyngeal region, optical median section. B. Vulval region. C. Female tail. D. Male tail. E. Female anterior end, surface view. F. Male anterior end, surface view. Scale bar = 20 µm.

Tables

Table 4. Measurements (in µm) of Diplopeltoides nudus (Gerlach, 1956), presented as mean and (range) for males and each female individual measurement separated with a semicolon.

Sex	Female	Male
Number of specimens	2	3
Body length	1135; 1004	1179 (1152–1225)
Body diameter (BD)	26; 27	23 (21–25)
Pharynx length	121; 117	119 (114–125)
Tail length	72; 71	81 (76–90)
Anal body diameter (ABD)	19; 18	21 (21–22)
a	43.3; 36.7	51.4 (45.9–59.7)
b	9.4; 8.6	9.9 (9.8–10.2)
c	15.8; 14.2	14.6 (13.6–15.2)
c’	3.7; 3.9	3.8 (3.5–4.2)
V or T (%)	54.7; 54.3	48.7 (47.9–49.5)
Labial region diameter	12.0; 10.5	10.8 (10.5–11.0)
Cephalic setae length	1.5; 1.5	1.0 (1.0–1.5)
Amphid from anterior end	5.5; 5.5	5.8 (5.0–7.0)
Dorsal amphid branch length	18.5; 17.0	18.9 (16.5–20.0)
Ventral amphid branch length	16.0; 14.5	17.3
Amphid width	6.0; 6.0	6.9 (6.0–7.5)
Nerve ring from anterior end	65; 63	65 (64–66)
Nerve ring from anterior end as % of pharynx length	54; 53	54 (53–55)
Secretory-excretory pore from ant. end	111; 102	108
Secretory-excretory pore from ant. end as % of pharynx length	92; 86	86
Anterior gonad length (to flexure)	124; 114	–
Posterior gonad length (to flexure)	152; 90	–
Vagina or spicules length	9; 9	37 (35–38)
Rectum or gubernaculum length	17; 12	10 (9–11)
Vagina length / BD	0.3; 0.3	–
Rectum or spicules length / ABD	0.9; 0.6	1.7 (1.6–1.8)