CC BY
8
two new nematode species of the genus EUTOBRILUS (nematoda, triplonchida) from lake baikal (russia)
Tatyana V. Naumova1* , Vladimir G. Gagarin2
1Limnological Institute Siberian Branch of the RAS, Russia 2Papanin Institute for Biology of Inland Waters RAS, Russia *e-mail: tvnaum@lin.irk.ru
Received: 04.10.2022. Revised: 22.12.2022. Accepted: 27.01.2023.
This paper describes and illustrates two new nematode species of the genus Eutobrilus found in Lake Baikal. Eutobrilus tsalolikhini sp. nov. is most similar to E. mirandus and E. obesus in body size and spicules length. It differs from E. mirandus in its thicker body, longer outer labial setae, larger stoma, and more supplements. It differs from E. obesus in a shorter tail, farther location of vulva from the anterior body end, longer outer labial setae, and more supplements. Eutobrilus olkhonensis sp. nov. is most similar to E. fortis and E. godlewskii in body size and supplements location but differs from both species in a thicker body, longer tail in males, shorter spicules, and fewer supplements.
Key words: diversity, free-living nematodes, morphology, taxonomy, Tobrilidae
Introduction
Lake Baikal is a fascinating freshwater body that is known throughout the world. Its shores and pure crystal clean water attract many tourists as well as experts and researchers. The ancient age of Lake Baikal (25-30 million years), the enormous depths of the water body (1637-1642 m) containing one fifth of the world's surface fresh water and its high oxygen saturation (up to 9.5 mg/L at the 1600-m depth point) make it a wonder of our planet. The unique environments of Lake Baikal inevitably provided favourable conditions for the formation of an abundant and diverse fauna, including over 2600 species with a high level of endemism (over 56%) (Timoshkin, 2001). According to the latest records, the fauna of free-living nematodes comprises 116 species, belonging to 32 genera, 16 families and eight orders (Naumova & Gagarin, 2019). These species are found on rocky, sandy, and silty substrates, occupying all depths from the splash zone (above the water edge) to the deep zones. In terms of abundance, nematodes often dominate other ben-thic groups. Eutobrilus Tsalolikhin, 1981 is one of the most well-known and diverse genera of the family Tobrilidae. At present, it contains 36 valid species (Andrassy, 2007; Gagarin & Naumova, 2011a,b, 2012, 2018; Naumova & Gagarin, 2021). In Lake Baikal, 17 valid species (including the new species described below) were identified, namely E. affectiosus Shoshin, 1988, E. anguiculus (Tsalolikhin, 1977), E. assimula-tus Shoshin, 1988, E. ayaensis Gagarin & Nau-
mova, 2018, E. brzeskii Gagarin & Naumova, 2012, E. differtus Shoshin, 1988, E. fortis (Tsalolikhin, 1972), E. grandipapillatus (Brakenhoff, 1914), E. godlewskii Naumova & Gagarin, 2021, E. longicaudatoides Gagarin & Naumova, 2011, E. mirabilis (Shoshina, 2003) Andrassy, 2007, E. mirandus Gagarin & Naumova, 2011, E. obesus Gagarin & Naumova, 2012, E. peregrinator Tsalolikhin, 1983, E. prodigious Shoshin, 1988, E. selengaensis (Tsalolikhin, 1977), E. stefanskii Gagarin & Naumova, 2018. The aim of this paper is to describe two new nematode species inhabiting Lake Baikal.
Material and Methods
The nematodes were collected in the littoral zone of Lake Baikal from the following sites: central basin of Lake Baikal (Maloye More Strait), Elginsky Bay (53.154010° N, 107.174021° E), 30-cm depth, sand, collected on 16.07.2018; central basin of Lake Baikal (Maloye More Strait), Olkhon Island, near Saraysky Beach (52.12865°-53.12670° N, 107.21023°-107.20789° E), 15-20-m depth, sand with mica, collected on 17.06.2021. The samples contained numerous free-living nema-todes, including both species described herein. Nematodes were preserved in 4% formaldehyde, tinted with Rose Bengal dye and mounted in glycerin on permanent slides (Williams & Williams, 1974; Ryss, 2003). All observations were made with the Olympus CX-21 and Nikon Eclipse 80i light microscopes with Nomarski DIC accesso-
ries. Images were taken using a Nikon DS-Fil digital camera and Intel Pentium Dual CPU E 2200 Processor Series for Desktop with the NIS-Elements D 3.2 programme for analysis and documentation of images from the preparations.
Results and Discussion
Phylum Nematoda Potts, 1931 Class Enoplea Inglis, 1983 Order Triplonchida Cobb, 1920 Family Tobrilidae de Coninck, 1965 Genus Eutobrilus Tsalolikhin, 1981 Type species. Eutobrilus grandipapillatus (Brakenhoff, 1914) Tsalolikhin, 1981 - Trilobus grandipapillatus Brakenhoff, 1914.
Diagnosis. It is made according to Andrassy (2007) and Holovachov & Shoshin (2014). The body length varies from 1.5 mm to 4.7 mm. Cuticle is smooth or very finely annulated. Buccal cavity is cup- or funnel-shaped, with an overlapping subventral pocket and teeth close to each other. Vagina is moderately strong. Spicules are comparatively short. Supplements are of 5 to 9 (rarely 13), echinate, protrusible; the first and last supplements are generally smaller than the others; two posterior supplements are often more remote from the others.
Taxonomy
Eutobrilus tsalolikhini Naumova & Gagarin sp. nov.
Type material. Holotype is male (slide reference number: 1506-3); two paratypes are males and two paratypes are females (slides reference number: 1506-2, 1506-5, 1509-2, 1509-3); they are deposited in the Helminthological Museum collection of the Centre for Parasitology, A.N. Se-vertsov Institute of Ecology and Evolution of the RAS (Moscow, Russia). Six paratypes are males and eight paratypes are females (slides reference number: 1504-1, 1504-2, 1504-3, 1504-4, 15045, 1505-4, 1505-5, 1508-1, 1508-2, 1508-3, 15084, 1508-5, 1516-4, 1516-5); they are deposited in the Limnological Institute, Siberian Branch of the RAS (Irkutsk, Russia).
Type locality and habitats. Russia, central basin of Lake Baikal (Maloye More Strait), Elgin-sky Bay. Samples were collected on 16.07.2018 (leg. T.V. Naumova). Individuals of the new species were found at 30-cm depth.
Etymology. The species is named in honour of the Russian scientist, nematologist, Professor, Dr. Sc. Semyon Ya. Tsalolikhin.
Description of males. Body is comparatively long and thin (Table 1, Fig. 1, Fig. 2). Cuticle is finely annulated; 2.0-|m thick. Body diameter at the pharynx base is 2.3-2.6 times wider than the labial region. Crystalloids are numerous. Somatic setae are rare and short, 4-5 |m long. Labial region is slightly offset from the adjacent body; lips are well developed. Six inner labial sensillae are papilliform. Six outer labial sensillae are in the shape of smooth, non-articulated setae, 18-21 |m long, 51-62% of the labial region width. Four cephalic sensillae are in the shape of thin and smooth setae are 10-12 |m long. Both circles of setae are drawn close together. Cheilostom is of average size. Buccal cavity is spacious, funnel-shaped, with thick walls. Dorsal pocket and its tooth are absent. Subventral pockets are located close to each other. Stoma is 1.0-1.1 times longer than labial region width. Amphidial fovea is cup-shaped, opening at the level of the buccal cavity. Pharynx is muscular, comparatively long, gradually expanding along the entire length. Cardial glands are large, rounded, 20-22 |m in diameter. Ventral gland, its canal, ampulla, and excretory pore are not seen. Testes are paired, opposed, located to the left of the intestine; anterior testis is outstretched, posterior testis is reflexed. Vas deferens is well developed. Spicules are slender, slightly curved, short, 1.2-1.4 times longer than the cloacal body diameter, apically bifurcate. Gubernaculum is in the shape of a straight «gutter», 27-30 |m long. Precloacal supplements are 8-11 in number, echinate, protrusible. Supplementary pads are armed with small thorns and one longer thorn. Ampullae contents are at the top of ampullae. Supplements are approximately identical in size and located almost equidistant from each other. The supplement closest to cloaca is at 50-82 |m away from it; supplement row is 450-650 |m long. Tail is slender, elongate-conical. Caudal glands are well developed; spinneret is present. Subterminal seta is absent.
Description of females. General morphology is similar to that of males in the structure of the cuticle and anterior body. Cardia is small, surrounded by three round glands. Prerectum is not observed. Rectum length is equal to or slightly greater than anal body diameter. Reproductive system is didelphic, amphidelphic. Ovaries are located to the left of the intestine, reflexed and comparatively short. Oocytes are numerous. Vulva is a transverse slit and equa-
torial. Vulval lips are not sclerotised and not contains numerous spermatozoa and 2-7 eggs,
protruding outside the body contour. Cuticular measuring 70-75 x 42-62 ^m. Tail is slender,
wrinkles near the vulva and vulva glands are long, elongate-conical. Caudal glands are well
not seen. Vagina is short, with thin walls. Uterus developed. Subterminal seta is absent.
Fig. 1. Holotype male and paratype female of Eutobrilus tsalolikhini sp. nov. Designations: A - Male anterior end; B -Supplement; C - Vulva region; D - Male tail; E - Female tail; F - Female reproductive system. Scale bars: A = 25 ^m; B = 15 ^m; C = 120 ^m; D, E = 45 ^m; F = 200 ^m.
Table 1. Morphometrics of males and females of Eutobrilus tsalolikhini sp. nov.
Characters Holotype male Paratypes
Males (n = 8) Females (n = 10)
range mean range mean
L, ^m 2397 2158-2433 2313 2442-4120 2805
a 31 25-31 28 20-40 26
b 4.7 4.2-4.7 4.5 4.2-5.5 4.5
c 15.0 15.0-18.3 16.8 12.7-15.9 14.2
c' 3.5 3.0-3.5 3.1 3.0-5.0 4.0
V, % - - - 46-51 48
Labial region diameter, ^m 33 33-36 34 39-45 42
Mid-body diameter, ^m 78 75-90 84 80-125 116
Anal or cloacal body diameter, ^m 45 40-47 44 44-65 50
Stoma (buccal cavity) length, ^m 35 33-36 35 40-45 42
Outer labial setae length, ^m 20 18-21 20 20-22 21
Cephalic setae length, ^m 12 10-12 11 10-12 11
Distance from the anterior body end to nerve ring, ^m 129 110-135 126 120-151 132
Pharynx length, ^m 512 488-550 519 558-745 621
Distance from the pharynx base to the vulva, ^m - - - 538-1288 726
Distance from the pharynx base to the cloaca, ^m 1725 1535-1750 1655 - -
Distance from the vulva to anus, ^m - - - 1025-1825 1260
Tail length, ^m 160 130-161 138 168-262 198
Spicules length, ^m 58 53-58 56 - -
Gubernaculum length, ^m 28 27-30 28 - -
Number of supplements 9 8-11 9 - -
Note: L - body length; a - ratio of body length to body width in its middle part; b - ratio of body length to pharynx length; c - ratio of body length to tail length; c' - ratio of tail length to body width at the anus or cloacal region; V - ratio of the distance from the anterior end of the body to the vulva to the total body length.
Fig. 2. Eutobrilus tsalolikhini sp. nov., light micrographs. Designations: A - Entire male; B - Entire female; C - Male anterior end; D - Male head; E - Female head; F - Female vulva region; G - Male supplement region; H - Male posterior end; I - Female posterior end. Scale bars: B = 200 |m; A, C = 100 |m; F = 50 |m; E, H, I = 20 |m; D, G = 10 |m.
Diagnosis. Eutobrilus tsalolikhini sp. nov. is characterised by a large body (2158-4120 |m long). Cuticle is finely annulated. Crystalloids are numerous in the body cavity. Inner labial sensillae are papil-liform. Six outer labial sensillae are in the shape of smooth, non-articulated setae, 18-22 |m long, 4762% of labial region width. Four cephalic sensillae in the shape of thin and smooth setae are 10-12 |m long. Buccal cavity is spacious funnel-shaped. Dorsal pocket and its tooth are absent. Subventral pockets are located close to each other. Spicules are slender, slightly curved, 53-58 |m long, 1.2-1.4 long as the cloacal body diameter. Gubernaculum is in the shape of straight «gutter». Precloacal supplements are 8-11 in number, echinate, protrusible. Ampullae contents are at the top ampullae. Tail is slender, long, elongate-conical. Subterminal seta is absent.
Differential diagnosis. Eutobrilus tsalolikhini sp. nov. is close to E. mirandus and E. obesus in body size and spicules length. The new species differs from E. mirandus by having a thicker body in males (a = 25-
31 vs. S a = 32-45), longer outer labial setae (18-22 |m vs. 10-13 |m) and stoma (33-45 |m vs. 25-31 |m), more posterior vulva (V = 46-51% vs. V = 2531%), number of supplements (8-11 vs. 6-7) and a different tail shape (Gagarin & Naumova, 2011a). Eutobrilus tsalolikhini sp. nov. differs from E. obesus in its shorter tail (c = 12.7-18.3 vs. c = 6.7-9.3), the more posterior location of the vulva from the anterior body end (V = 46-51% vs. V = 40-46%), longer outer labial setae (18-22 |m vs. 8-10 |m), number of supplements (8-11 vs. 7-8), the thicker tail (vs. very thin tail in E. obesus) (Gagarin & Naumova, 2012).
Eutobrilus olkhonensis Naumova & Gagarin sp. nov.
Type material. Holotype is male (slide reference number: 1668-3); two paratypes are males and four paratypes are females (slides reference number: 16681, 1668-2, 1706-1, 1706-2, 1706-3, 1706-4); they are deposited in the Helminthological Museum collection of the Center for Parasitology, A.N. Severtsov Institute of Ecology and Evolution of the RAS (Moscow, Russia). Six paratypes are males and six paratypes are females (slides reference number: 1667-1, 16672, 1667-3, 1667-4, 1667-5, 1669-1, 1669-2, 1708-1, 1708-3, 1710-4, 1723-1, 1723-4); they are deposited in the Limnological Institute, Siberian Branch of the RAS (Irkutsk, Russia).
Type locality and habitats. Russia, central basin of Lake Baikal (Maloye More Strait), Olkhon Island, near Saraysky Beach. Samples were collected on 17.06.2021 (leg. T.V. Naumova). Individuals of the new species were found at 15-20-m depth.
Etymology. The specific epithet means from «Olkhon Island», the type locality name.
Description of males. Body is comparatively short and thick (Table 2, Fig. 3, Fig. 4). Cuticle is faintly annulated, 2-|m thick. Somatic setae are sparse, short, 4-7 |m long. Crystalloids are absent. Labial region is slightly offset from the adjacent body; lips are well developed. Six inner labial sensillae are papilliform. Six outer labial sensillae in the shape of smooth non-articulated setae are 7-8 |m long, 26-30% of labial region width. Four cephalic sensillae are in shape of smooth setae. Cheilostom is of average size. Buccal cavity is spacious, funnel-shaped, with thick walls. Dorsal pocket and its tooth are absent. Subventral pockets are located close to each other or less often overlap each other. Stoma is 1.1-1.2 times longer than labial region width. Amphidial fovea is cup-shaped, opening at the level of the buccal cavity. Pharynx is muscular, comparatively long, gradually expanding along the entire length. Cardial glands are large, rounded. Ventral gland, its canal ampulla and excretory pore are not
seen. Testes are paired, opposed, situated to the left of the intestine; anterior testis is outstretched, posterior testis reflexed. Vas deferens is well developed. Spicules are slender, slightly curved, 55-58 |im long, 1.1-1.3 times longer than the cloacal body diameter. Gubernaculum is in the shape of "gutter" 25-27 |im long. Precloacal supplements are echinate, located in two groups (2 + 3), supplement closest to the cloaca smaller than others. Supplementary pads are armed with small thorns and one longer and thicker thorn. Ampulla contents are at the top of the ampullae. Tail is slender, long, elongate-conical, with subterminal seta. Caudal glands and spinneret are well developed.
Description of females. General morphology is similar to that of males in the structure of cuticle and the anterior body end. Six inner labial sensillae are papilliform. Six outer labial sensillae are in the shape of smooth, non-articulated setae, 8-10 |im long; four cephalic sensillae are smooth, 4-5 |im long. Cardia is small, surrounded by three round glands. Prerectum is not observed. Rectum length is equal to or slightly less than anal body diameter. Reproductive system is didelphic. Ovaries are located to the left of intestine, reflexed, comparatively short. Oocytes are numerous. Vulva is transverse slit, located in mid-body. Vulval lips are not sclerotised, not protruding outside the
body contour. Cuticular wrinkles near vulva and vulva glands are not seen. Vagina is comparatively long, with thick walls. Uterus contains numerous spermatozoa and 1-2 eggs, measuring 58-75 x 35-55 ^m. Tail is slender, elongate-conical, with subterminal seta. Caudal glands and spinneret are well developed.
Diagnosis. Eutobrilus olkhonensis sp. nov. is characterised by its small size (body 1251-1570 |im long). Cuticle is faintly annulated. Crystalloids are absent. Inner labial sensillae are papilliform. Six outer labial sensillae are in the shape of smooth, non-articulated setae, 7-10 |im long, 21-30% of labial region width. Four cephalic sensillae are in the shape of thin and smooth setae 4-5 |im long. Buccal cavity is spacious, funnel-shaped. Dorsal pocket and its tooth are absent. Subventral pockets are located close to each other or less often overlap each other. Spicules are slender, slightly curved, short (55-58 |im), 1.1-1.2 times longer than cloacal body diameter. Gubernac-ulum is in the shape of «gutter» with curved distal end. Precloacal supplements are echinate are in two groups (2 + 3) and the supplements closest to the cloaca smaller than the outers. Supplementary pads are armed with small thorns and one longer and thicker thorn. Ampulla contents are at its top. Tail is slender, elongate-conical, with subterminal seta.
Fig. 3. Eutobrilus olkhonensis sp. nov. Designations: A - Male anterior end; B - Supplement; C - Female tail; D - Vulva region; E - Male posterior end; F - Female reproductive system. Scale bars: A = 20 ^m; B = 15 ^m; C = 50 ^m; D, F = 100 ^m; E = 80 ^m.
Table 2. Morphometries of males and females of Eutobrilus olkhonensis sp. nov.
Characters Holotype male Paratypes
Males (n = 8) Females (n = 10)
range mean range mean
L, pm 1456 1373-1597 1461 1251-1570 1394
a 19 17-21 18 12-19 15
b 4.5 4.3-4.8 4.5 3.9-4.4 4.1
c 10.2 8.7-10.4 9.8 6.7-8.0 7.3
c' 2.9 2.6-3.4 3.0 3.1-4.3 3.8
V, % - - - 46-51 49
labial region diameter, pm 27 26-29 28 30-38 33
Mid-body diameter, pm 75 73-87 79 73-122 96
Anal or cloacal body diameter, pm 50 45-54 49 45-65 51
Stoma (buccal cavity) length, pm 30 28-31 29 30-37 33
Outer labial setae length, pm 7 7-8 7 8-10 9
Cephalic setae length, pm 4 4 4 4-5 4
Distance from the anterior body end to nerve ring, pm 100 100-125 111 110-130 116
Pharynx length, pm 325 288-388 321 310-380 337
Distance from the pharynx base to the vulva, pm - - - 300-425 349
Distance from the pharynx base to the cloaca, pm 988 950-1105 990 - -
Distance from the vulva to anus, pm - - - 458-580 518
Tail length, pm 143 135-167 149 175-210 191
Spicules length, pm 56 55-58 56 - -
Gubernaculum length, pm 25 25-27 26 - -
Number of supplements 5 5 5 - -
Note: L - body length; a - ratio of body length to body width in its middle part; b - ratio of body length to pharynx length; c - ratio of body length to tail length; c' - ratio of tail length to body width at the anus or cloacal region; V - ratio of the distance from the anterior end of the body to the vulva to the total body length.
Differential diagnosis. Eutobrilus olkhonensis sp. nov. is most similar to E. fortis (Tsalolikhin, 1972) and E. godlewskii Naumova & Gagarin, 2021 in body size and supplement arrangement. The new species differs from E. fortis in its thicker body (a = 12-21 vs. a = 22-35), longer tail in males (S c = 8.7-10.4 vs. S c = 10.4-14.0), longer outer labial setae (7-10 pm long vs. 2 pm long), shorter spicules (55-58 pm long vs. 62 pm long), and fewer supplements (5(2 + 3) vs. 6(2 + 4)) (Tsalolikhin, 1972). Eutobrilus olkhonensis sp. nov. differs from E. godlewskii by having a thicker body (a = 12-21 vs. a = 23-34), longer tail in males (S c = 8.7-10.4 vs. S c = 12.6-14.5), shorter spicules (55-58 pm vs. 63-70 pm), and fewer supplements (5(2 + 3) vs. 6-7 (2 + 4-5)) (Naumova & Gagarin, 2021).
The combination of the shape and structure of stoma (pockets less separated from each other), the simple vagina and the protrusible supplements characterise the genus Eutobrilus within the family Tobr-ilidae. Regarding the number of species, it is the largest genus in this family (Andrassy, 2007). The genus occurs in Europe, Asia, Africa, North America, Australia, and Antarctica. In the genus Eutobrilus, more than half of the species (19 of 36) are inhabitants of Lake Baikal, where they occur in the depth range of 0-1610 m as well as in the splash zone (0.5 m above the water edge). Most of the species (15 of 19) are endemic (Naumova & Gagarin, 2019).
We believe that the knowledge on the species diversity of Baikal representatives of the genus Eu-
Fig. 4. Eutobrilus olkhonensis sp. nov., light micrographs. Designations: A - Entire male; B - Entire female; C - Male anterior end; D - Male head; E - Female head; F - Female vulva region; G - Male cloaca region; H - Male posterior end; I - Female posterior end. Scale bars: A, B = 100 pm; F = 50 pm; C, H, I = 20 pm; D, E, G = 10 pm.
tobrilus is far from complete awaiting new exciting contributions. The use of molecular-genetic approaches would enable researchers to highlight the phylogeny of this group and estimate the evolution rate within the genus. These are the objectives of future investigations.
Acknowledgements
The study was supported by the Russian state projects №121032300180-7 and №121051100109-1. The authors thank Dr. Vladimir A. Gusakov (Papanin Institute for Biology of Inland Waters RAS, Russia) for assistance in preparing the micro-photographs. The English version has been proofread by Julia M. Vitushenko.
References
Andrássy I. 2007. Free-living Nematodes of Hungary (Nema-toda Errantia). Vol. 2. Budapest: Hungarian Natural History Museum and Systematic Zoology Research Group of the Hungarian Academy of Sciences. 496 p. Gagarin VG., Naumova T.V. 2011a. Two nematode species of the family Tobrilidae (Enoplida) De Coninck, 1965 from Lake Baikal, Russia. Zootaxa 2815: 59-68. DOI: 10.11646/zootaxa.2815.1.1.4 Gagarin VG., Naumova T.V 2011b. Prodorylaimus filamentus sp. n. and Eutobrilus longicaudatoides sp. n. (Nematoda) from Lake Baikal, Russia. Zootaxa 3103: 57-68. DOI: 10.11646/zootaxa.3103.1.3 Gagarin VG., Naumova TV 2012. Eutobrilus obesus sp. nov. and E. brzeskii sp. nov. (Nematoda: Triplonchida: Tobrili-
dae) from Lake Baikal, Russia. Annates Zoologici 62(2): 317-324. DOI: 10.3161/000345412X652855 Gagarin VG., Naumova T.V. 2018. Two new species of Eutobrilus Tsalolikhin, 1981 (Nematoda: Triplonchida) from Lake Baikal, Russia. Annales Zoologici 68(4): 741-748. DOI: 10.3161/00034541ANZ2018.68.4.002 Holovachov O., Shoshin A. 2014. Order Triplonchida Cobb, 1919. In: A. Schmidt-Rhaesa (Ed.): Handbook of Zoology: Gastrotricha, Cycloneuralia and Gnathifera. Vol. 2: Nematoda. Berlin, Boston: De Gruyter. P. 251-276. Naumova T.V, Gagarin VG. 2019. Review of the free-living Nematode (Nematoda) fauna of Lake Baikal. Zootaxa 4608(1): 101-118. DOI: 10.11646/zootaxa.4608.1.5 Naumova TV, Gagarin V.G. 2021. Eutobrilus godlewskii sp. nov. and Tobrilus gigas sp. nov. (Nematoda: Triplonchida) from Lake Baikal, Russia. Annales Zoologici 71(2): 213223. DOI: 10.3161/00034541ANZ2021.71.2.001 Ryss A.Y. 2003. Express technique to prepare permanent collection slides of nematodes. Zoosystematica Rossica 11(2): 257-260.
Timoshkin O.A. 2001. Lake Baikal: diversity of fauna, problems of its immiscibility and origin, ecology and «exotic» communities. In: Index of Animal Species Inhabiting Lake Baikal and Its Catchment Area: In 2 vol. Vol. 1: Lake Baikal, Book 1. Novosibirsk: Nauka. P. 74-113. Tsalolikhin S.Ya. 1972. New species of free-living nematodes from Lake Baikal. Zoologicheskii Zhurnal 51: 15591563. [In Russian] Williams D.D., Williams N.E. 1974. A counterstaining technique for use in sorting benthic samples. Limnology and Oceanography 19(1): 152-154. DOI: 10.4319/ lo.1974.19.1.0152
два новых вида нематод рода еитовяниз
(nematoda, triplonchida) из озера байкал (россия)
Т. В. Наумова1" , В. Г. Гагарин2
1 Лимнологический институт СО РАН, Россия 2Институт биологии внутренних вод имени И.Д. Папанина РАН, Россия
*е-таИ: tvnaum@lin.irk.ru
В статье приведены иллюстрированные описания двух новых видов нематод рода ЕШоЬгПш, найденные в оз. Байкал. ЕШоЬгИш tsalolikhini sp. поу. наиболее близок к Е. т^апёж и Е. oЬesus по длине тела и длине спикул. Он отличается от Е. т^апёж более толстым телом, более длинными наружными губными щетинками, более крупной стомой и большим количеством супплементов. От Е. oЬesus отличается более коротким хвостом, дальним положением вульвы от переднего конца тела, более длинными наружными губными щетинками, большим количеством супплементов. ЕШоЬгИт olkhonensis sp. поу. наиболее близок к Е. fortis и Е. godlewskii по длине тела и расположению супплементов, но отличается от обоих видов более толстым телом, более длинным хвостом у самцов, короткими спикулами и меньшим количеством супплементов.
Ключевые слова: ТоЬпШае, морфология, разнообразие, свободноживущие нематоды, таксономия
