Diplopeltoides asetosus (Juario, 1974) 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 : 10-13

Diplopeltoides asetosus (Juario, 1974) comb. nov.

Fig. 4 ; Table 2

Diagnosis

Diplopeltoides asetosus is characterised by a body of 0.76–1.19 mm long; cuticle without longitudinal striation; cuticularised plate absent; cephalic sensilla setiform, 3.5–7.0 µm long; amphidial fovea an inverted U-shape, 14–19 µm long and 6–9 µm wide; wide space between amphidial branches punctuated or crenate; secretory-excretory pore located opposite to basal pharyngeal swelling; tail subcylindrical with rounded terminus; testes outstretched; spicules 17–31 µm long, strongly curved, with dorsally bent manubrium and subcylindrical shaft; gubernaculum plate-like, with caudal apophyses.

Material examined

SWEDEN: 1 ♀, Skagerrak, 58°20′06″ N, 11°09′24″ E, muddy sediment from 53 m deep, 9 Aug. 2011, O. Holovachov leg. (SMNH-159532); 2 ♀♀, 2 ♂♂, Skagerrak, 58°15′25″ N, 11°27′30″ E, soft mud from 30 m deep, 11 Aug. 2011, O. Holovachov leg. (SMNH-159533-534); 1 ♀, Skagerrak, 58°15′37″ N, 11°27′43″ E, soft mud from 44 m deep, 11 Aug. 2011, O. Holovachov leg. (SMNH-159534).

Description

Adult

Body cylindrical, posteriorly tapering in tail region, straight or ventrally curved upon fixation, more so in the posterior part of males. Cuticle coarsely annulated along entire body, except for smooth anterior end and terminal part of the tail; annules 1.5–2.5 µm wide at mid-body region; longitudinal striation not observed under the light microscope. Somatic setae visible on tail. Labial region bluntly rounded, lips fused. Cuticularised plate underlying cephalic cuticle around amphid absent. Inner and outer labial sensilla not seen. Cephalic sensilla setiform, equal to 0.3–0.6 labial region diameters in length, their bases are located 3–3.5 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. Wide space between amphidial branches (amphidial shield) strongly cuticularised, punctuated or crenate. Stoma very small, its cuticularised lining is 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 ovoid, its body adjacent and ventrosublateral to anterior part of intestine. Tail subcylindrical with rounded terminus. Caudal glands opening via three separate openings, spinneret absent.

Female

Reproductive system didelphic, amphidelphic, reflexed; ovary branches symmetrical. Anterior ovary situated to right of intestine; posterior ovary situated to left of intestine. Vulva at or immediately posterior to mid-body. Vagina straight, 0.3 of the vulval body diameter, with developed sphincter muscle at its proximal part; pars refringens vaginae absent. Intrauterine egg not seen; sperm is visible in the uterus. Rectum short, 0.7–1 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 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. asetosus is similar to the type specimens in general morphology and measurements, except for the relatively broader amphid and longer spicules (26–31 µm vs 17 µm (along chord) in the text of the original description or 21 µm as re-measured along curved median line using the original drawing).

Figures

Fig. 4. Diplopeltoides asetosus (Juario, 1974) comb. nov. A. Vulval region. B. Female tail. C. Male tail. D. Female anterior end, surface view. E. Male anterior end, surface view. F. Female pharyngeal region, optical median section. Scale bar = 20 µm.

Tables

Table 2. Measurements (in µm) of Diplopeltoides asetosus (Juario, 1974) comb. nov., presented as mean and (range) for females and each male individual measurement separated with a semicolon; “?” indicates that the character can not be observed or measured.

Sex	Female	Male
Number of specimens	4	2
Body length	993 (866–1190)	1050; 1064
Body diameter (BD)	24 (21–28)	21; 21
Pharynx length	103 (100–107)	104; 100
Tail length	84 (71–96)	83; 89
Anal body diameter (ABD)	16 (15–17)	16; 18
a	42.0 (31.7–52.2)	51.2; 51.9
b	9.6 (8.6–11.1)	10.1; 10.6
c	11.9 (10.6–12.4)	12.6; 12.0
c’	5.1 (4.1–5.7)	5.2; 4.9
V or T (%)	52.8 (50.9–54.5)	?; 51.5
Labial region diameter	10.7 (10.0–12.0)	11.0; 10.5
Cephalic setae length	4.8 (3.5–5.5)	6.0; 5.0
Amphid from anterior end	4.8 (4.0–6.0)	3.5; 5.5
Dorsal amphid branch length	16.6 (14.0–18.5)	18.0; 16.5
Ventral amphid branch length	14.5 (12.0–16.5)	16.0; 14.5
Amphid width	7.4 (6.0–8.0)	7.5; 7.5
Nerve ring from anterior end	61 (58–64)	?; 55
Nerve ring from anterior end as % of pharynx length	60 (58-62)	?; 55
Secretory-excretory pore from ant. end	90 (87–94)	96; 86
Secretory-excretory pore from ant. end as % of pharynx length	87 (85-91)	92; 85
Anterior gonad length (to flexure)	112 (46–154)	–
Posterior gonad length (to flexure)	121 (60–159)	–
Vagina or spicules length	7 (7–8)	31; 26
Rectum or gubernaculum length	14 (12–17)	4; 5
Vagina length / BD	0.3	–
Rectum or spicules length / ABD	0.8 (0.7–1.0)	1.9; 1.4