Diplopeltoides bulbosus ( Vitiello, 1972 ) Holovachov & Boström, 2017

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 : 13-17

Diplopeltoides bulbosus ( Vitiello, 1972) comb. nov.

Figs 5–6 , 11A ; Table 3

Diagnosis

Diplopeltoides bulbosus is characterised by by a body of 1.12–1.58 mm long; cuticle with longitudinal striation visible only under SEM; cuticularised plate absent; cephalic sensilla papilliform, 1–2 µm long; amphidial fovea an inverted U-shape, 21–28 µm long and 7–11 µm wide, with fine striation; narrow space between amphidial branches not cuticularised; secretory-excretory pore located opposite to basal pharyngeal swelling; tail cylindrical or clavate with bluntly rounded terminus; testes outstretched; spicules 34–50 µm long, strongly curved, with dorsally bent manubrium and subcylindrical, gradually narrowing shaft; gubernaculum plate-like, with or without caudal apophysis.

Material examined

SWEDEN: 3 ♀♀, 2 ♂♂, Skagerrak , 58°19′15.6″–20.9″ N, 10°29′33.5″–34.0″ E, soft bottom 352– 374 m deep, 10 Oct. 2012, “ Inventering Bratten ” leg. ( SMNH-159537 ) ; 1 ♂, soft bottom 232–240 m deep, Skagerrak , 58°27′36.7″–43.3″ N, 10°32′52.0″–59.4″ E, 12 Oct. 2012, “ Inventering Bratten ” leg. ( SMNH-159538 ) ; 7 ♀♀ (used for SEM), 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 .

Description

Adult

Body cylindrical, posteriorly tapering in the tail region, straight or variously curved upon fixation. Cuticle coarsely annulated along entire body, except for smooth anterior end and terminal part of tail; annules 2.5–3 µm wide at mid-body region; longitudinal striation not observed under light microscope, but distinct under scanning electron microscope, covers annules over most of body length, except for anteriormost and posteriormost parts. Somatic setae present along pharyngeal region and 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 3.5–6 µm from anterior end. Amphids similar in shape and size between sexes: amphidial fovea an inverted U-shape with ventral branch longer than dorsal branch; tip of ventral branch bent to dorsal side. Interior of amphideal fovea with fine striation visible under light and scanning electron microscopes. Narrow space between amphidial branches (amphidial shield) not cuticularised. Stoma very small, its cuticularised lining uniform with lining of 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. Secretory-excretory 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 cylindrical or clavate, 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 (usually) or left (rarely) of intestine; posterior ovary situated to either left (usually) or right (rarely) of intestine. Vulva pore-like, located posterior to mid-body. Vagina straight, 0.3–0.4 of vulval body diameter, with thick walls and developed sphincter muscle at proximal part; pars

refringens vaginae absent. Intrauterine egg not seen; sperm is visible in uterus. Rectum short, 0.7–0.9 of 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 caudal apophysis that is variable in size and can be indistinct in some specimens. Caudal setae present, arranged in subventral and subdorsal rows, but difficult to observe.

Remarks

The recently collected population of D. bulbosus is similar to type specimens in general morphology, measurements and shape of amphids, except for the spicule length. Vitiello (1972) stated in the original description that the spicules are 25 µm long, compared to 45–50 µm in our specimens. Measured from the drawings in the original description, the spicule length of the type specimen appears to be closer to 34 µm.

Figures

Fig. 5. Diplopeltoides bulbosus (Vitiello, 1972) comb. nov. A. Female anterior end, surface view. B. Female pharyngeal region, optical median section. C. Vulval region. D. Female tail. E. Male anterior end, surface view. F. Male tail. Scale bar = 20 µm.

Fig. 6. Diplopeltoides bulbosus (Vitiello, 1972) comb. nov. SEM micrographs of females. A–B. Anterior end, right sublateral view (arrow points at the anterior edge of longitudinal striation of cuticle). C. Female tail (arrow points at the posterior edge of the longitudinal striation of the cuticle). D. Anterior end, left sublateral view. E. Vulval region, ventrosublateral view. F. Vulval region, lateral view. G. Tail terminus (arrows point at openings of caudal glands. Scale bars: A–G = 5 µm.

Fig. 11. Light microscopy images of anterior ends. A. Diplopeltoides bulbosus (Vitiello, 1972) comb. nov., female, amphid. — B–C. Diplopeltoides grandis sp. nov., holotype, female. B. Amphid. C. Cuticularised plate. Scale bars: A–C = 20 µm.

Tables

Table 3. Measurements (in µm) of Diplopeltoides bulbosus (Vitiello, 1972) comb. nov., presented as mean±s.d. (standard deviation) and (range) or mean and (range).

Sex	Female	Male
Number of specimens	10	3
Body length	1411±82 (1277–1573)	1363 (1159–1501)
Body diameter (BD)	41±3 (38–45)	33 (29–38)
Pharynx length	131±6 (122–140)	133 (124–140)
Tail length	79±5 (72–86)	86 (75–94)
Anal body diameter (ABD)	30±2 (26–34)	29 (26–32)
a	34.8±2.4 (31.6–38.6)	40.8 (39.9–41.8)
b	10.8±0.8 (9.1–11.8)	10.3 (9.3–11.3)
c	18.0±1.4 (16.1–20.3)	15.9 (15.3–16.9)
c’	2.6±0.3 (2.3–3.0)	3.0 (2.8–3.3)
V or T (%)	60.2±2.5 (56.2–64.3)	44.7 (43.2–45.9)
Labial region diameter	13.4±0.9 (12.5–14.5)	13.6 (13.0–14.0)
Cephalic setae length	1.4±0.3 (1.0–2.0)	1.5
Amphid from anterior end	6.7±1.1 (5.0–8.0)	5.5 (5.0–6.0)
Dorsal amphid branch length	22.3±0.9 (21.5–24.0)	26.7 (25.5–27.5)
Ventral amphid branch length	22.1±1.3 (21.0–25.0)	26.2 (25.5–27.0)
Amphid width	9.3±0.8 (8.0–10.5)	10.7 (10.5–11.0)
Nerve ring from anterior end	74±3 (68–79)	79 (78–81)
Nerve ring from anterior end as % of pharynx length	56±2 (54–60)	58
Secretory-excretory pore from ant. end	115±5 (106–120)	119 (107–128)
Secretory-excretory pore from ant. end as % of pharynx length	88±2 (84–91)	90 (86–92)
Anterior gonad length (to flexure)	122±24 (86–159)	–
Posterior gonad length (to flexure)	127±26 (93–155)	–
Vagina or spicules length	13±2 (10–15)	47 (45–50)
Rectum or gubernaculum length	26±3 (21–30)	10
Vagina length / BD	0.3 (0.3–0.4)	–
Rectum or spicules length / ABD	0.8±0.1 (0.7–0.9)	1.6 (1.5–1.9)