Tobrilus juliae, Naumova & Gagarin, 2019

Naumova, Tatyana V. & Gagarin, Vladimir G., 2019, Two new nematode species of the genus Tobrilus Andrássy, 1959 (Nematoda, Triplonchida) from Lake Baikal, Russia, European Journal of Taxonomy 579, pp. 1-13 : 7-10

Tobrilus juliae sp. nov.

urn:lsid:zoobank.org:act:34D3DBF2-8273-410C-8CA0-CAC1279ACA77

Figs 3–4 , Table 2 (morphometric)

Diagnosis

Tobrilus juliae sp. nov. is characterized by a 1800–2386 µm long body; cuticle smooth under light microscope; crystalloids absent; inner labial sensillae papilliform; six outer labial sensillae in the shape of smooth, non-articulated setae 4–6 µm long for males (24–35% of labial region width) and 5–6 µm long for females (28–38% of labial region width); four cephalic sensillae on the shape of thin and smooth setae 3–4 µm long for males and 2–4 µm long for females; buccal cavity spacious, barrelshaped; dorsal pocket and it tooth absent; both subventral pockets overlapping adjacent to each other. Spicules slightly curved, 45–50 µm long, 1.2–1.5 long as the cloacal body diameter; gubernaculum in the shape of ‘gutter’; precloacal supplements 6–7 in number, small, submerged; tail short, elongateconical, with terminal seta.

Type material

Holotype

RUSSIA • ♂; Lake Baikal (Southern basin), near Cape Berezovy; 51°30′11″ N, 104°32′33″ E; 5 m depth; 6 Sep. 2016; bodies of dead sponges Lubomirskia baicalensis collected by divers; HM RAS slide reference number 102/70.

Paratypes

RUSSIA • 9 ♂♂, 10 ♀♀; same collection data as for holotype; LIN-SB; 1 ♀; same collection data as for holotype; HM RAS slide reference number 102/70 (1390-1) .

Etymology

The species named in gratitude to Ms Julia Zvereva.

Description

Male

Body comparatively long and thin. Cuticle smooth under light microscope, 1.0– 1.5 µm thick. Body diameter at the posterior pharynx end 2.1–2.5 times the width of the labial region. Crystalloids absent. Somatic setae rare and short, 3–4 µm long. Labial region only slightly offset from the adjacent body; lips well developed. Six inner labial sensillae papilliform. Six outer labial sensillae in the shape of smooth, non-articulated setae 4–6 µm long, 24–35% of labial region width. Four cephalic sensillae in the shape of thin and smooth setae 3–4 µm long. Both circles of setae drawn close together. Cheilostoma of the average size. Buccal cavity spacious, barrel-shaped, with thick walls. Dorsal pocket and it tooth absent. Both subventral pockets overlapping adjacent to each other. Its teeth small, close to each other (distance ~ 3 µm). Stoma 1.0–1.2 as long as labial region width. Amphidial fovea cup-shaped, opening at the level of buccal cavity. Pharynx muscular, comparatively long, expending gradually along entire length. Cardiac glands large, rounded, 15–17 µm in diameter. Ventral gland, its canal, ampulla and excretory pore not seen.

Testes paired, opposed, situated to the left of intestine; anterior testis outstretched, posterior testis reflexed. Vas deferens well developed. Spicules slightly curved, comparatively short, 1.2–1.5 times as long as the cloacal body diameter, apically bifurcate. Gubernaculum in the shape of ‘gutter’, 43–47% of the spicule length. Precloacal supplements 6–7 in number, small, submerged. Supplement ampulla flattened, its contents concentrated at ampulla base. Supplement cap absent. Central thorn protruding slightly above cuticle. Supplements approximately identical in size and situated about equidistant from each other. The closest to cloaca supplement at 11–20 µm away from it; supplement row 175–290 µm long. Tail short, elongate-conical, with terminal seta 3–5 µm long. Caudal glands well developed; spinneret in the shape of a short, conical tube.

Female

General morphology similar to that of males in structure of cuticle and anterior body end. Six outer labial sensillae in the shape of smooth setae 5–6 µm long, 28–38% of labial region width; four cephalic sensillae in the shape of thin, smooth setae 2–4 µm long. Cardia small, surrounded by three round glands. Rectum length equal to or slightly greater than anal body diameter. Reproductive system didelphic, amphidelphic. Ovaries situated to the left of intestine, reflexed and comparatively short. Oocytes numerous. Vulva a transverse slit and situated slightly posterior to mid-body. Vulval lips not sclerotized and not protruding outside the body contour. Cuticular wrinkles around vulva and vulva glands not observed. Vagina short. Uterus containing numerous spermatozoa and 1– 2 eggs, measuring 70–72 × 40–43 µm. Tail short, elongate-conical, with subterminal seta. Caudal glands well developed.

Remarks

Tobrilus juliae sp. nov. is most similar to T. securus and T. saprophagus in body size. From the first species it differs in the thinner body (a = 41–63 vs a = 25–40 in T. securus ), shorter tail (c = 11.3– 23.4, c ʹ = 2.4–6.1 vs c = 6.7–8.4, c ʹ = 6.3–9.3 in T. securus ), comparatively shorter outer labial setae (24–35% of labial region width vs 40–45% of labial region width in T. securus ) and shorter spicules (45–50 µm long vs 52–58 µm long in T. securus ) ( Gagarin & Naumova 2011). From the second species T. juliae sp. nov. differs in the thinner body (a = 41–63 vs a = 30–43 in T. saprophagus ), shorter tail in males (♂ c = 17.5–23.4 vs ♂ c = 11.5–16.7 in T. saprophagus ) and shorter outer labial setae (4–7 µm long, 24–35% labial region width vs 10–12 µm long, 37–46% of labial region width in T. saprophagus ( Naumova & Gagarin 2017) .

Figures

Fig. 3. Tobrilus juliae sp. nov. A. Male anterior end. B. Female vulva region. C. Male pharyngeal region. D. Female posterior body end. E. Male posterior body end. Scale bars: A = 15 µm; B = 50 µm; C = 100 µm; D = 40 µm; E = 30 µm.

Fig. 4. Tobrilus juliae sp. nov., light micrographs. A. Entire male. B. Entire female. C. Male pharyngeal region. D. Female anterior end. E. Male anterior end. F. Female vulva region. G. Male posterior body end. H. Female posterior body end. Scale bars: A–B = 250 µm; C, F, H = 50 µm; D–E, G = 10 µm.