Tobrilus methanus sp. n. and Tripyla posolskii sp. n. (Nematoda, Triplonchida) from Lake Baikal, Russia Author Gagarin, Vladimir G. Author Naumova, Tatyana V. text Zootaxa 2016 4196 1 95 106 journal article 10.11646/zootaxa.4196.1.5 9ec8ba28-5318-4094-936c-ac274030379c 1175-5326 167698 AF21F5ED-8734-4D9A-8BD5-5B5B7AD57994 Tripyla posolskii sp. n. ( Figs 3 , 4 ; Table 3 ) Type material. Holotype male, slide reference number 102/57, deposited in the helminthological museum of the Russian Academy of Sciences ( RAS ), Institute of Ecology and Evolution , Center for Parasitology , RAS ( Moscow , Russia ) . Paratypes . Twelve males and twelve females deposited in the collection of the Limnological Institute Siberian Branch of the Russian Academy of Sciences ( Irkutsk , Russia ). Type locality . Region of Posol’skaya Banka elevation ( South Baikal , N 52°02ʹ08ʺ, E 105°50ʹ36ʺ), Lake Baikal , Russia , depth 500 m , silt. Nematodes were collected on 3 July 2015 . Etymology . The specific epithet means “from Posol’skaya Banka”, the type locality. Description. Male . Body of average size and average thickness. Cuticle annulated. Somatic setae and crystalloids absent. Lips three. Labial region narrow, not offset. Inner labial sensillae papilliform. Six outer labial sensillae in the shape of large and stout papillae 5–6 µm long, 21–23% of labial region width. Four cephalic sensillae in the shape of thin setae the same length. Both rings of sensillae are arranged at a considerable distance (7.5–8.5 µm) from each other. Stoma not developed. Small tooth located in internal part of pharynx at distance 21– 26 µm from anterior body end. Pharynx muscular, expanding gradually towards its base. Cardia small, surrounded by 3 oval glands. Renette, renette canal, ampulla and excretory pore not observed. Amphidial fovea cup-shaped, 6– 8 µm wide, located at distance 14–20 µm from anterior body end. Testes paired, opposed, situated to the left of intestine; anterior testis outstretched, posterior testis reflexed. Vas deferens well developed. Spicules comparatively short and stout, 1.0–1.2 times as long as the cloacal body diameter, with well developed, roundish capitulum. Gubernaculum in the shape of a thin plate, 18–27 µm long. Spicules and gubernaculum are contained in muscular sac. Supplementary organs in the shape of small, hardly visible papillae, 14–19 in number; 5–6 supplementary organs located in pharynx region. Tail long with conical proximal and cylindrical distal portions. Distal portion 1.7–1.9 times as long as its proximal portion. Caudal glands and spinneret well developed. Female . General appearance, structure of cuticle and anterior of body similar to males. Cuticle annulated. Somatic setae and crystalloids are absent. Labial region narrow, not offset from adjacent body. Inner labial sensillae papilliform. Six outer labial sensillae in the shape of large and stout papillae 5–6 µm long. Four cephalic sensillae in the shape of thin setae the same length. Both rings sensillae are arranged at distance 7–9 µm from each other. Stoma not developed. Small tooth located in internal part of pharynx at distance 24–33 µm from anterior body end. Pharynx muscular, expanding gradually towards its base. Cardia small, surrounded by three oval glands. Amphidial fovea cup-shaped, located at distance 17–30 µm from anterior body end. 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. Vulva a transverse slit and situated to mid-body. Vulval lips not sclerotized and not protruding outside the body contour. Vagina short, with thin walls. Uterus containing numerous spermatozoids and 1– 3 eggs measuring 121–150 x 37 –50 µm. Tail long, with conical proximal and cylindrical distal portions. Distal portion 1.4–1.7 times as long as its proximal portion. Caudal glands and spinneret well developed. FIGURE 3 . Tripyla posolskii sp. n. Holotype male and paratype female. A: male, entire body; B: male head; C: vulva region; D: female tail; E: male tail. Scale bars: A—200 µm; C–E—60 µm; B—25 µm. FIGURE 4 . Tripyla posolskii sp. n. Paratype male and female. A: male, entire body; B: female, entire body; C: male, anterior body end; D: male head; E: female head; F: vulva region; G: cloaca region; H: male tail; I: female tail. Scale bars: A, B—200 µm; C, H—100 µm; F, I—50 µm; D, G—20 µm; E—10 µm. Diagnosis . Body of the average size and average thickness (L = 1548–2078 µm, a = 23–36). Cuticle annulated. Somatic setae and crystalloids absent. Lips tree. Labial region narrow, not off set. Inner labial sensillae papilliform. Six outer labial sensillae in the shape of large and stout papillae 5–6 µm long. Four cephalic sensillae in the shape of thin setae the same length. Both rings of sensillae are arranged on considerable distance (7–9 µm) from each other. Stoma not developed. Small tooth located in internal part of pharynx at distance 21–33 µm from anterior body end. Amphidial fovea cup-shaped, located at distance 14–30 µm from anterior body end. Spicules comparatively short and stout, 1.0–1.2 times as long as cloacal body diameter. Gubernaculum in the shape of a thin plate, 18–27 µm long. Supplements small, hardly visible papillae, 14–19 in number. 5–6 supplementary organs located in pharynx region. Tail long, with conical proximal and cylindrical distal portions. Distal portion 1.4–1.9 times as long as its proximal portion. TABLE 3. Morphometrics of Tripyla posolskii sp. n. Characters Holotype Paratype males (n = 12) Paratype females (n = 12) male range mean range mean Differential diagnosis. At present, the genus Tripyla Bastian, 1865 contain 20–24 valid species ( Andrássy 2007 , Zullini 2006 ). Four species have been found in the Lake Baikal: T. dybowskii Tsalolikhin, 1976 , T. filicaudata de Man, 1880 , T. setifera Bütschli, 1873 and T. infia Brzeski & Winiszewska-Ślipińska, 1993 ( Gagarin & Naumova 2012b , 2013 ; Naumova et al. 2012; Shoshin & Tsalolikhin 2001 ; Tsalolikhin 1976 ). T. posolskii sp. n. morphologically is close to T. dybowskii , but differs from it in the shorter body (L = 1548–2078 µm vs L = 2400– 3530 µm in T. dybowskii ), shorter tail ( c = 4.7–7.2, cʹ = 5.8–7.9 vs c = 2.5–4.8, cʹ = 7.3–11.9) and shorter spicules (47–57 µm long vs 85–92 µm long) ( Gagarin & Naumova 2013 , Tsalolikhin 1972 ).