Tobrilus saprophagus, 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 : 135-138

Tobrilus saprophagus sp. n.

( Figs 1 , 2 ; Table 1)

Type material. HolotyPe male, slide reference number 102/58, dePosited in the Helminthological Museum of the Russian Academy of Sciences ( RAS), Institute of Ecology and Evolution, Center for Parasitology RAS (Moscow, Russia).

Paratypes. Two males and four females dePosited in the Helminthological Museum of the Russian Academy of Sciences ( RAS), Institute of Ecology and Evolution , Center for Parasitology RAS (Moscow, Russia). Seven males and nine females dePosited in the collection of Limnological Institute Siberian Branch of the Russian Academy of Sciences (Irkutsk, Russia).

Type locality. Bolshie Koty Bay oPPosite the Chernaya Valley (N 51°31'53", E 105°03'07"), 6–7 m dePth.

Etymology. The sPecific ePithet means “saProPhage”, as this nematode was found in the bodies of dead sPonges.

Description. Male. Body comParatively long and thin. Cuticle smooth under light microscoPe, 2.0–2.5 µm thick. Crystalloids absent; somatic setae rare and short 6–7 µm long. Labial region slightly offset from the adjacent body; liPs well develoPed. Body diameter at the Posterior Pharynx end 2.4–2.8 times the width of the labial region. Inner labial sensillae PaPilliform. Six outer labial sensillae in the shaPe of articulate setae 10–11 µm long, 37–46 % of labial region width. Four cePhalic sensillae in the shaPe of thin and smooth setae 5.0–6.5 µm long. Body circles of setae drawn close together. Cheilostom comParatively large. Buccal cavity sPacious, funnel-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. Stoma 1.1–1.4 times as long as labial region width. AmPhidial fovea cuP-shaPed, oPening at the level of buccal cavity. Pharynx muscular, comParatively long, exPanding gradually along entire length. Cardiac glands large, rounded, 20–23 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 thick, slightly curved, short, 0.9–1.0 times as long as the cloacal body diameter, aPically bifurcate. Gubernaculum in the shaPe of a thin Plate, 47–58% of the sPicule length. Precloacal suPPlements 6–7 in number, small, submerged. SuPPlement amPulla flattened, contents concentrated at amPulla base. SuPPlement caP absent. Central thorn Protruding slightly above cuticle. SuPPlements aPProximately identifical in size and situated about equidistant from each other. Distance from cloaca to first suPPlement 20–35 µm; suPPlement row 201–317 µm long. Tail slender, elongate-conical, with subterminal setae. 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. Cuticle smooth. Labial region slightly offset from the adjacent body; liPs well develoPed. Inner labial sensillae PaPilliform, outer labial sensillae in the shaPe of articulated setae; cePhalic sensillae in the shaPe of smooth setae. Both circles of setae drawn close together. Cheilostom small; buccal cavity sPacious, funnel-shaPed. Both subventral Pockets overlaPPing adjacent to each other. Teeth in Pockets small. Pharynx muscular, exPanding gradually towards base. Cardia small, surrounded by 3 round glands. Prerectum not observed. 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 anterior to midbody. Vulva liPs not sclerotized and not Protruding outside the body contour. Cuticular wrinkles round vulva and vulva glands not seen. Vagina short, with thick walls. Uterus containing numerous sPermatozoa and 1– 4 eggs, measuring 70– 92 x 42–60 µm. Tail slender, long, elongate-conical, with subterminal setae. Caudal glands well develoPed.

Diagnosis. Body comParatively long and thin (L = 2033–2688 µm, a = 30–43). Cuticle smooth. Crystalloids absent. Outer labial setae articulate; cePhalic setae smooth. Both circles of setae drawn close together. Outer labial setae as long as 37–46% of labial region width. Cheilostom small. Buccal cavity sPacious, funnel-shaPed. Both subventral Pockets overlaPPing adjacent to each other. Stoma 1.1–1.4 as long as labial region width. SPicules thick, slightly curved, short, 0.9–1.0 as long as the cloacal body diameter. Gubernaculum in the shaPe of a thin Plate. Precloacal suPPlements 6–7 in number, vesiculate, small, submerged under cuticle excePt for short thorn Protruding beyond cuticle. Tail slender, long, elongate-conical with subterminal setae.

Differential diagnosis. Tobrilus saprophagus sp. n. is similar to T. bekmanae Tsalolikhin, 1975 and T. securus Gagarin & Naumova, 2011 in body size and in stoma shaPe and structure. From the first sPecies it differs in the less slender tail (♂ cʹ = 2.9–3.9, ♀ cʹ = 3.5–6.8 vs ♂ cʹ = 6, ♀ cʹ = 9 in T. bekmanae ), narrower labial region (24–30 µm vs 35–38 µm in T. bekmanae ), shorter outer labial setae (10–12 µm vs 13–18 µm in T. bekmanae ) and shorter stoma (25–32 µm vs 40–56 µm in T. bekmanae ) ( Tsalolikhin 1975). From T. securus it differs in the shorter and less slender tail (♂ c = 11.5–16.1, cʹ = 2.9–3.9, ♀ c = 8.8–13.1, cʹ = 3.5–6.8 vs ♂ c = 6.7–8.4, cʹ = 6.3–9.3, ♀ c = 7.1– 8.4, cʹ = 6.6–7.7 in T. securus ), longer outer labial setae (10–12 µm vs 6.5–9.0 µm in T. securus ) and shorter sPicules (45–48 µm vs 52–58 µm in T. securus ) ( Gagarin & Naumova 2011d).

Diagnosis (modified after Andrássy 2007). Body 1.1 to 5.3 mm long. Outer labial setae, with rare excePtions, long (45–65% of head diameter). AmPhidial fovea at level of stoma. Buccal cavity funnel-shaPed, anterior Pocket jointed to the funnel-Part of stoma or just Posterior to that, Posterior Pocket seParate, and teeth distant from each other. Vagina normal or slightly swollen. SPicules comParatively short. SuPPlements 5 to 13, echinate, Protruded or semi-submerged.

Type species. E. meyli Tsalolikhin, 1981

Other valid sPecies: E. allophysis ( Steiner, 1919) Gagarin, 1991 ; E. elephas ( Andrássy, 1964) Zullini, 2006 ; E. flagellatus ( Andrássy, 1963) Tsalolikhin, 1981 ; E. heptapapillatus ( Joubert & Heyns, 1979) Zullini, 2006 ; E. husmanni ( Altherr, 1958) Zullini, 2006 ; E. medius ( Schneider, 1916) Tsalolikhin, 2001 ; E. parvipapillatus ( Kreis, 1932) Tsalolikhin, 1981 ; E. sablensis ( Ebsary, 1982) Tsalolikhin, 2001 ; E. scalensis ( Schneider, 1925) Andrássy, 2007 ; E. setosus ( Altherr, 1963) Tsalolikhin, 1981 ; E. steineri (Micoletzky, 1925) Andrássy, 2007 , E. interstitialis sp. n. MorPhometrics of these sPecies are given in Table 2.

Baikalian sPecies of the genus Epitobrilus were unknown until now. Tobrilus medius from Lake Baikal was described and illustrated by S. Ya. Tsalolikhin (1980), but has been re-assigned to Eutobrilus peregrinator Tsalolikhin, 1983 .

Figures

FIGURE 2. Tobrilus saprophagus 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: cloaca region; I: male tail; J: female tail. Scale bars:B—500 µm; A—250 µm; C—100µm; D, J—50 µm; E, H, I—20 µm; F, G—10 µm.

FIGURE1. Tobrilus saprophagus sp. n. Holotype male and paratype female.A:male head;B: vulva region; C: female tail; D: male tail; E: supplement.Scale bars: B, C, D—50 µm; A—25 µm; E—10 µm.