Diplopeltoides suecicus, 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 : 5-10

Diplopeltoides suecicus sp. nov.

urn:lsid:zoobank.org:act:BD6CBB55-4DF6-4E17-802B-093C3DE95BD5

Figs 1–3 ; Table 1

Diagnosis

Diplopeltoides suecicus sp. nov. is characterised by a body of 0.82–1.02 mm long; cuticle with longitudinal striation visible only under SEM; cuticularised plate underlying cephalic cuticle around amphid present; cephalic sensilla setiform, 4–6 µm long; amphidial fovea an inverted U-shape, 14– 21 µm long and 6–9 µm wide; wide space between amphidial branches areolated; secretory-excretory pore located opposite to basal pharyngeal swelling; tail subcylindrical with bluntly rounded terminus; testes outstretched; spicules 27–31 µm long, strongly curved, with weakly defined manubrium and subcylindrical shaft; gubernaculum plate-like, with caudal apophyses.

Etymology

The specific epithet “ suecicus ” (masculine) – Swedish, refers to the country where the new species was first discovered.

Type material

Holotype

SWEDEN: ♂, Gullmarn Fjord near Fiskebäckskil, 58°15′25″ N, 11°27′30″ E, soft mud from 30 m deep, 11 Aug. 2011, O. Holovachov leg. ( SMNH Type-8840 ).

Paratypes

SWEDEN: 4 ♀♀, 1 ♂, Gullmarn Fjord near Fiskebäckskil, 58°15′25″ N, 11°27′30″ E, soft mud from 30 m deep, 11 Aug. 2011, O. Holovachov leg. ( SMNH Type-8841); 1 ♀, 2 ♂♂, Gullmarn Fjord near Fiskebäckskil, 58°15′37″ N, 11°27′43″ E, soft mud from 44 m, 11 Aug. 2011, O. Holovachov leg. ( SMNH Type-8842).

Description

Adult

Body cylindrical, posteriorly tapering in the tail region, straight or weakly ventrally curved upon fixation. Cuticle coarsely annulated along entire body, except for visually smooth anterior end (faint annulation is visible under the scanning electron microscope) 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 but distinct under the scanning electron microscope, covers annules over entire body length. Somatic setae visible on tail. Labial region bluntly rounded, lips fused. Cuticularised plate underlying cephalic cuticle around amphid, extending from the level of the anteriormost edge of amphid to the posteriormost edge of amphid, 17– 21.5 µm long and 12–14.5 µm wide at its base; cuticular plates are connected with each other on ventral and on dorsal sides. Inner labial sensilla not seen; outer labial sensilla small papilliform, located on the anterior surface of lips. Cephalic sensilla setiform, equal to 0.5–0.8 labial region diameters in length, their bases are located 1.5–2 µm from anterior end. Amphids similar in shape and size between sexes: amphidial fovea an inverted U-shape with its dorsal branch longer than ventral branch. Wide space between amphidial branches (amphidial shield) strongly cuticularised and areolated. Stoma very small, its cuticularised lining is uniform with the 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. Secretory-excretory system present; secretory-excretory pore located along the ventral body line opposite to basal pharyngeal swelling; secretory-excretory duct very short, leading from pore to ampulla; renette cell small, its body adjacent and ventral to anterior part of intestine. 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 either right or left of intestine. Vulva pore-like, located at or immediately posterior to mid-body. Vagina straight, 0.2–0.3 of the vulval body diameter, with developed sphincter muscle at its proximal part; pars refringens vaginae absent. Intrauterine egg not seen; sperm is often present in the uterus. Rectum short, 0.7–0.9 of the corresponding body diameter long.

Male

Reproductive system diorchic, both testes outstretched. Spicules paired and symmetrical, strongly curved, with weakly defined 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

Diplopeltoides suecicus sp. nov. is most similar to D. axayacatli and D. grandis sp. nov. in having strongly developed cuticularised plate and amphid with wide and ornamented interamphideal shield. The new species differs from D. axayacatli in the shape of the amphid (loop-shaped vs hook-shaped in D. axayacatli ), shorter cephalic setae (4–6 µm vs 15–20 µm in D. axayacatli ), gubernaculum with strong apophyses (vs without apophyses in D. axayacatli ) and shorter tail (c’ = 2.8–3.7 vs 5.0–6.0 in D. axayacatli ); it differs from D. grandis sp. nov. in shorter body (0.82–1.02 mm vs 2.06 mm in D. grandis sp. nov.) and shorter cephalic setae (4–6 µm vs 18.5 µm in D. grandis sp. nov.).

Figures

Fig. 1. Diplopeltoides suecicus sp. nov. A. Anterior part of the female reproductive system. B. Female anterior end, surface view. C. Male anterior end, surface view. D. Female pharyngeal region, optical median section. E. Female tail. F. Male tail. Scale bar = 20 µm.

Fig. 2. Diplopeltoides suecicus sp. nov. SEM micrographs. A, C–D. Male. B, E. Female. A. Anterior end, apical view (arrows point at outer labial sensilla). B–D. Anterior end, left sublateral view. E. Vulval region. Scale bars: A–E = 5 µm.

Fig. 3. Diplopeltoides suecicus sp. nov. SEM micrographs. A. Male cloacal region, lateral view. B. Male cloacal region, ventrosubventral view. C. Male tail, lateral view. D–E. Female tail, ventrosublateral view. Scale bars: A–E = 5 µm.

Tables

Table 1. Measurements (in µm) of Diplopeltoides suecicus sp. nov., presented as mean and (range).

Sex	Holotype male	Female	Male
Number of specimens	1	5	4
Body length	932	896 (821–980)	963 (932–1018)
Body diameter (BD)	23	32 (30–33)	22 (19–24)
Pharynx length	87	87 (81–92)	88 (87–90)
Tail length	67	60 (57–67)	73 (67–83)
Anal body diameter (ABD)	19	20 (18–21)	21 (19–23)
a	40.9	28.1 (24.8–33.1)	44.8 (39.1–49.8)
b	10.8	10.3 (9.6–10.9)	10.9 (10.4–11.3)
c	13.8	14.9 (14.2–15.9)	13.2 (12.2–13.9)
c’	3.5	3.1 (2.8–3.4)	3.6 (3.5–3.7)
V or T (%)	52.0	52.9 (50.0–55.3)	73.0 (52.0–92.8)
Labial region diameter	8.0	8.6 (8.0–9.0)	8.1 (7.5–8.0)
Cephalic setae length	6.0	5.0 (4.0–6.0)	5.7 (5.5–6.0)
Amphid from anterior end	7.5	5.8 (5.5–6.0)	6.7 (5.5–7.5)
Dorsal amphid branch length	17.0	15.5 (14.0–16.5)	17.9 (15.0–21.0)
Ventral amphid branch length	15.0	14.5 (13.0–17.0)	17.1 (15.0–19.0)
Amphid width	8.0	6.6 (6.0–7.0)	7.8 (6.0–9.0)
Nerve ring from anterior end	56	55 (51–63)	56
Nerve ring from anterior end as % of pharynx length	65	64 (56–73)	65
Secretory-excretory pore from ant. end	74	75 (63–82)	80 (74–84)
Secretory-excretory pore from ant. end as % of pharynx length	86	86 (78–92)	90 (86–94)
Anterior gonad length (to flexure)	–	104 (83–114)	–
Posterior gonad length (to flexure)	–	113 (93–124)	–
Vagina or spicules length	27	8 (6–10)	29 (27–31)
Rectum or gubernaculum length	9	16 (14–18)	8 (6–9)
Vagina length / BD	–	0.2 (0.2–0.3)	–
Rectum or spicules / ABD	1.4	0.8 (0.7–0.9)	1.4 (1.3–1.5)