Epitobrilus interstitialis, Naumova & Gagarin, 2017

Naumova, Tatyana V. & Gagarin, Vladimir G., 2017, Tobrilus saprophagus sp. n. and Epitobrilus interstitialis sp. n. (Nematoda, Triplonchida) from Lake Baikal, Russia, Zootaxa 4353 (1), pp. 133-145 : 139-143

Epitobrilus interstitialis sp. n.

( Figs 3 , 4 ; Table 2, 3)

Type material. HolotyPe male, slide reference number 102/59, dePosited in the Helminthological Museum of the Russian Academy of Sciences ( RAS), Institute of Ecology and Evolution, Center for Parasitology RAS (Moscow, Russia).

Paratypes. Fourteen males and eleven females dePosited in the collection of the Limnological Institute , Siberian Branch of the Russian Academy of Sciences (Irkutsk, Russia)

Type locality. Lake Baikal, Bolshie Koty Bay, oPPosite the Biological Station of the Limnological Institute. Also collected in Bolshie Koty Bay oPPosite the Varnachka Valley (N 51°32'30", E 105°03'44") and Listvyanichny Bay oPPosite NerPinary (seals Pool) (N51°30'16", E104°31'23"). Sand in the shore sPlash zone.

Etymology. The sPecific ePithet means “from sandy sPlash zone, interstitial”.

Description. Male. Body comParatively long and thin. Cuticle finely annulated, 2.0–2.5 µm thick at mid-body. Cuticular rings narrow, Poorly visible. Somatic setae sParse and short, 6–8 µm long. Labial region slightly off set from the adjacent body; liPs well develoPed. Body diameter at the Posterior Pharynx end 1.5–1.8 times the width of the labial region. Inner labial sensillae PaPilliform. Six outer labial sensillae in the shaPe of thin, articulate setae 33–37 µm long, 55–70% of labial region width. Four cePhalic sensillae in the shaPe of thin and smooth setae 12–15 µm long. Both circles of setae drawn close together. Cheilostom comParatively thin. Buccal cavity sPacious, funnel-shaPed, with thick walls. Dorsal Pocket and its tooth absent. Anterior subventral Pocket only slightly seParated from buccal cavity. Posterior subventral Pocket more seParated from anterior subventral Pocket. Subventral teeth in both Pockets comParatively small, located from each other at distance 15–18 µm. Stoma length aPProximately equal to width of labial region. AmPhidial fovea cuP-shaPed, located at the level of buccal cavity. Pharynx muscular, comParatively long, exPanding gradually along its entire length. Cardiac gland large, rounded, 30–40 µm in diameter. Ventral gland and canal, amPulla, and excretory Pore not observed.

Testes Paired, oPPosed, situated to the left of intestine; anterior testis outstretched, Posterior testis reflexed. Vas deferens well develoPed. SPicules comParatively short and almost straight, 1.2–1.4 times as long as the cloacal body diameter. CaPitulum absent; aPical end of sPicules bifurcated. Gubernaculum in the shaPe of a thin Plate, 27.4–38.5% of sPicule length. Precloacal suPPlement echinate, Protruded, 6–7 in number. SuPPlement amPulla slightly flattened, its contents concentrated at amPulla base. SuPPlement Pad large, armed with numerous (aPProximately 40–50) small thorns; caP comParatively small, with large central thorn bearing a lateral aPoPhysis. SuPPlements about identical size and located aPProximately equidistant from each other. The nearest suPPlement to the cloaca located at the level of the Proximal end of the sPicules. SuPPlement row 372–542 µm long. Tail slender, elongate-conical, with subterminal seta. Three caudal glands well develoPed, oPening through a short sPinneret.

Female. General morPhology similar to that of males in cuticle structure and anterior body, but with slightly longer body and longer tail. Cuticle finely annulated. LiPs well develoPed. Inner labial sensillae PaPilliform. Outer labial sensillae and cePhalic sensillae in the shaPe of thin setae. Outer labial setae articulated and as long as 55– 70% of labial region width. Both circles of setae drawn close together. Cheilostom small; buccal cavity sPacious, funnel-shaPed. Dorsal Pocket and tooth absent. Anterior subventral Pocket only slightly seParated from buccal cavity. Posterior subventral Pocket well seParated from anterior subventral Pocket. Subventral teeth in both Pockets comParatively small and located 15–20 µm aPart. AmPhidial fovea cuP-shaPed, located at the level of buccal cavity. Pharynx muscular, exPanding gradually along its entire length. Cardiac gland large. 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 at level of mid-body. Vulva liPs not sclerotized and not Protruding beyond the body contour. Advulval cuticular wrinkles and vulval glands not seen. Vagina short, with thick walls. Uterus containing numerous sPermatozoa and 1–5 intrauterine eggs, measuring 82–105 x 50 –70 µm. Tail elongate-conical, with subterminal setae. Three caudal glands Present, oPening through a short, tube-like sPinneret.

Diagnosis. Body comParatively long and thin (L = 4108–5972 µm, a = 39–65). Cuticle finely annulated. Crystalloids absent. Outer labial sensillae and cePhalic sensillae in the shaPe of setae. Outer labial setae articulate and are as long as 55–70% of labial region diameter. Both circles of setae drawn close together. Cheilostom small; buccal cavity sPacious, funnel-shaPed. Dorsal Pocket and its tooth absent. Anterior subventral Pocket only slightly seParated from buccal cavity; Posterior subventral Pocket distinctly seParate from anterior subventral Pocket. Vulva a transverse slit, situated at about mid-body. Males with comParatively short, almost straight sPicules. SPicules bifurcate aPically. Gubernaculum in the shaPe of a thin Plate. Precloacal suPPlement echinate, Protruded, 6–7 in number. SuPPlement amPulla slightly flattened, contents concentrated at amPulla base. SuPPlement Pad large, armed with numerous small thorns. CaP comParatively small, with a large central thorn bearing a lateral aPoPhysis. All suPPlements nearly identical in size and located aPProximately equidistant from each outer. Tail slender, long, with subterminal setae.

Differential diagnosis. Epitobrilus interstitialis sP. n. is the largest in the genus Epitobrilus ( Table 2). It is morPhologically close to E. steineri (Micoletzky, 1925) Andrássy, 2007 , but differs from it in the longer body (♂ L = 4.75–5.29 mm vs ♂ L = 2.14–3.35 mm in E. steineri ), longer tail (♂ c = 13.4–16.8 vs ♂ c = 21.5–32.2 in E. steineri ), longer outer labial setae (27–40 µm long, 56–65% of labial region diameter vs 22–25 µm long, 45–55% of labial region diameter in E. steineri ) and longer sPicules (73–78 µm vs 51–71 µm in E. steineri (Micoletzky 1925, Tsalolikhin 1983, Gagarin 1993).

Figures

FIGURE 3. Epitobrilus interstitialis sp. n. Holotype male and paratype female. A:male head; B: vulva region; C: spicule and gubernaculum;D:supplement;E:female tail; F:male tail.Scalebars:B,E—90 µm; F—60 µm; A—40 µm; C—30 µm; D—15 µm.

FIGURE 4. Epitobrilus interstitialis sp. n. Holotype male, paratype male and female. A: male, entire body; B: female, entire body; C: male, anterior body end; D: vulva region; E, F: male head; G: female head; H: male, body at supplement region; I: male posterior body end; J: female tail.Scale bars:A, B—500 µm; C—200µm; D, H—100 µm; G, I, J—50 µm; E, F—20 µm.