Paratrilobus tankhoyensis, Naumova & Gagarin, 2020

Naumova, Tatyana V. & Gagarin, Vladimir G., 2020, Two new nematode species of the genus Paratrilobus Micoletzky, 1922 (Nematoda, Triplonchida) from the water area of Lake Baikal (Russia), European Journal of Taxonomy 723, pp. 159-172 : 161-165

Paratrilobus tankhoyensis sp. nov.

urn:lsid:zoobank.org:act:D13C061E-EE0E-4A58-B706-3E4256774FFF

Figs 1–2 , Table 1

Diagnosis

Paratrilobus tankhoyensis sp. nov. is characterized by a 3687–5463 µm long body; cuticle smooth under light microscope; crystalloids absent; inner labial sensillae in shape of short and thick setae 6–10 µm long; six outer labial sensillae in shape of smooth non-articulated setae 27–33 µm long, 54–67% of labial region width for males and 44–56% for females; four cephalic sensillae in shape of thin and smooth setae 12–15 µm long; buccal cavity spacious, barrel-shaped. One pocket merged with buccal cavity; two small teeth located in stoma base. Spicules comparatively thin and long (70–76 µm in length), 1.2–1.6 times as long as cloacal body diameter; gubernaculum in shape of ‘gutter’; precloacal supplements 6–7 in number, comparatively large, echinate; ‘cap’ and ‘shoulder’ well developed; supplemental ampulla comparatively large; its contents located in top part of ampulla; first and last supplements smaller than others; tail elongate-conical, comparatively thick, with subterminal seta.

Etymology

The species epithet means ‘from Tankhoy’, the type locality name.

Material examined

Holotype RUSSIA • ♂; Lake Baikal water area, Pereyomnaya River estuary , near Tankhoy railway station; 51.568452° N, 105.166531° E; 10 cm depth; 19 Jul. 2018; T.V. Naumova leg.; sand; HM RAS, slide

102/71 ( 1538-2 ).

Paratypes

RUSSIA • 1 ♂, 2 ♀♀; same collection data as for the holotype; T.V. Naumova leg.; HM RAS, slide 102/71 ( 1538-1 , 1538-3 , 1538-4 ) • 8 ♂♂, 8 ♀♀ same collection data as for the holotype; T.V. Naumova leg.; LIN–SB .

Description

Male

Body comparatively long, thin. Cuticle smooth under light microscope, 1.5–2.0 µm thick. Body diameter at posterior pharynx end 1.3–1.4 times as large as width of labial region. Crystalloids absent. Somatic setae sparse, short, 8–11 µm long. Labial region slightly offset from adjacent body; lips well developed. Six inner labial sensillae in shape of thick, short setae, 6–9 µm long. Six outer labial sensillae in shape of smooth non-articulated setae, long 54–67% of labial region width. Four cephalic sensillae in shape of thin, smooth setae. Cheilostom of average size. Buccal cavity spacious, barrel-shaped, with thick walls. One pocket offset from buccal cavity, on its base two small teeth. Stoma 0.9 times as long as labial region width. Amphidial fovea cup-shaped, opening at level of buccal cavity. Pharynx muscular, comparatively long, expanding gradually along entire length. Cardiac glands large, rounded, 22–25 µm in diameter. Ventral gland, its canal, ampulla, excretory pore not seen.

Testes paired, situated to left of intestine; anterior testis outstretched, posterior testis reflexed. Vas deferens well developed. Spicules comparatively thin, slightly curved, long, 1.2–1.6 times as long as cloacal body diameter. Gubernaculum in shape of ‘gutter’, 46–50% of spicule length. Precloacal supplements 6–7 in number, first, last supplements smaller than others. Supplement ampulla comparatively large, its contents located in top part of ampulla. Supplements comparatively large, echinate, ‘cap’, ‘shoulder’ well developed. Supplement row 475–588 µm long. Precloacal supplement located at spicules level. Tail elongate-conical, comparatively thick, with subterminal seta. Caudal glands well developed; spinneret in shape of short conical tube.

Female

General morphology similar to males in structure of cuticle, anterior body end. Six inner labial sensillae in shape of thick and short setae, 8–10 µm long. Outer labial sensillae in shape of smooth non-articulated setae, long 44–56% of labial region width. Cardia small, surrounded by three round glands. Prerectum not observed. Rectum length equal to or slightly less than anal body diameter. Reproductive system didelphic, amphidelphic. Ovaries situated to left of intestine, reflexed, comparatively short. Oocytes numerous. Vulva transverse slit, situated to mid-body or slightly anterior to mid-body. Vulval lips not sclerotized, not protruding outside body contour. Cuticular wrinkles around vulva, vulva glands not seen. Vagina short, with thick walls. Uterus containing numerous spermatozoa, 1– 2 eggs, measuring 112–132 × 52–80 µm. Tail elongate-conical, comparatively thick, with subterminal seta. Caudal glands well developed.

Remarks

Paratrilobus tankhoyensis sp. nov. is most similar to P. expugnator (Tsalolichin, 1976) in body size (Tsalolichin 1976). The new species differs from it in the comparatively thin body (a = 57–71 vs a = 32–44 in P. expugnator ), shorter and thicker tail (c = 23–38, cʹ = 2.3–3.7 vs c = 8.2–10.4, cʹ = 5.0– 7.5 in P. expugnator ), shorter stoma (stoma length 45–55 µm vs 70–80 µm long in P. expugnator ), and shorter spicules (spicules length 70–76 µm vs 90 µm long in P. expugnator ) (Tsalolichin 1976).

Figures

Fig. 1. Paratrilobus tankhoyensis sp. nov. A. Male anterior end. B. Female posterior end. C. Female vulva region. D. Male posterior body end. A, D: holotype (HM RAS 102/71 1538-2); B–C: paratype (HM RAS 102/71 1538-1). Scale bars: A = 30 µm; B = 60 µm; C = 80 µm; D = 40 µm.

Fig. 2. Paratrilobus tankhoyensis sp. nov., light micrographs. A. Entire male. B. Entire female. C. Male pharyngeal region. D. Male anterior end. E. Female anterior end. F. Female vulva region. G. Male cloacal region. H. Male precloacal supplement. I. Male posterior body end. J. Female posterior body end. A, H–I: holotype (HM RAS 102/71 1538-2); B, E, J: paratype (HM RAS 102/71 1538-3); C–D, G: paratype (HM RAS 102/71 1538-4), F: paratype (HM RAS 102/71 1538-1). Scale bars: A–B = 500 µm; C–E = 20 µm; F, I–J = 50 µm; G–H = 10 µm.