Allodorylaimus baikalensis, Naumova & Gagarin, 2021

Naumova, Tatyana V. & Gagarin, Vladimir G., 2021, Mesodorylaimus ushkaniensis sp. n. and Allodorylaimus baikalensis sp. n (Nematoda, Dorylaimida) from Lake Baikal, Russia, Zootaxa 4985 (2), pp. 285-293 : 289-292

Allodorylaimus baikalensis sp. n.

( Figs 3 , 4 ; Table 2)

Type material. Holotype male, inventory slide number 102/73, deposited in the nematode collection of the Helminthological Museum of the Russian Academy of Sciences (RAS), Institute of Ecology and Evolution , Center for Parasitology RAS (Moscow, Russia)

Paratypes. Six males and five mature females deposited in the nematode collection of the Limnological Institute , Siberian Branch of the Russian Academy of Sciences (Irkutsk, Russia)

Measurements. Table 2.

Type locality. Lake Baikal, Siberia, Russia, Bolshoy Ushkaniy Island, depth 3.0– 8.2 m, silt and stones. Collected on 15 June 2014 and 27–28 September 2016.

Etymology. The specific epithet means “from Lake Baikal”.

Description. Male. Body comparatively large, thin. Cuticle smooth and thin, without longitudinal ridges. Lateral pores not visible. Lips well developed; labial papillae distinct. Labial region offset from the adjacent body. Amphidial fovea cup-like, situated at the base of the lips. Odontostyle straight and slender, 1.1–1.2 times the labial region diameter; its aperture occupying 28–31% of its length. Odontophore rod-like, 0.5–0.6 times as long as odontostyle. Guiding ring single. Pharynx muscular, expanding gradually along its whole length. Cardia conoid, muscular, surrounded with intestinal tissue.

Testes paired, opposed. Spicules dorylaimoid, 1.3–1.5 times cloacal body diameter in length, with two spindleshaped lateral guiding pieces. 9–12 spaced, papilloid supplements anterior to cloaca; no precloacal space. Prerectum long, 4.2–5.0 cloacal body diameters long, intestinal-prerectum junction located in the region of the supplement series. Tail hooked, strongly curved ventrally, distal end pointed.

Female. General morphology similar to that of males in structure of cuticle and anterior body end. Reproductive system didelphic, amphidelphic. Ovaries comparatively long; oocytes numerous, arranged as a double and then a single row. Vulva a longitudinal slit, situated slightly anterior to mid-body. One to five prominent papillae arranged anterior and posterior to vulva. Vagina with muscular walls, occupying 30–40% of corresponding body width; pars proximalis vaginae in the shape of thin tube; pars refringens vaginae consisting of two round sclerotizations; pars distalis vaginae very short. Uterus spacious, filled with small rounded spermatozoa and containing 1– 2 eggs measuring 62–81x 21–30 µm. Rectum 1.0–1.3 times as long as anal body diameter; prerectum 2.3–3.0 times as long as anal body diameter. Tail hooked, strongly ventrally curved, terminus pointed.

Diagnosis. Body comparatively long and thin (L = 1360–1755 µm, a = 27–44); cuticle smooth; labial region offset from the adjacent body; odontostyle straight and slender, 15–18 µm long, 1.1–1.2 times the labial region diameter; aperture occupying 28–31% of its length; odontophore 9–11 µm long; guiding ring single; vulval slit longitudinal; uterus spacious, with numerous sperm and 1– 2 eggs, measuring 62–81x 21–30 µm; spicules 44–50 µm long, dorylaimoid: 9–12 spaced papilloid precloacal supplements; precloacal space absent; prerectum in males long, intestinal-prerectum junction located in the region of supplement row. Male and female tails are similar, hookshaped, strongly curved ventrally, with pointed distal end.

Differential diagnosis. At present the genus Allodorylaimus Andrássy, 1986 contain 29 valid species ( Vinciguerra 2006, Andrássy 2009, Gagarin & Serikova 2007). Allodorylaimus baikalensis sp. n. is morphologically close to A. tarkoenensis ( Andrássy, 1959) Andrássy 1986 , but differs in the longer body (♀♀ L = 1460–1750 µm, ♂♂ L = 1360–1755 µm vs ♀♀ L = 1290–1340 µm, ♂ L = 1109 µm in A. tarkoenensis ), comparatively longer tail (♀♀ cʹ = 1.9–3.2, ♂♂ cʹ = 1.6–2.6 vs ♀♀ cʹ = 1.5, ♂ cʹ = 1.3), longer spicules (44–50 µm long vs 39.2 µm long in A. tarkoenensis ), and comparatively longer prerectum in females (2.3–3.0 times as long as anal body diameter vs 2.0 times as long as anal body diameter in A. tarkoenensis ) ( Andrássy 1959).

Figures

FIGURE 3. Allodorylaimus baikalensis sp. n. Holotype male and paratype female.A: male, entire body; B: male head; C: vulva region; D: female, posterior body end; E: male, posterior body end. Scale bars: A—100 µm; C, E—50 µm; D—30 µm; B—10 µm

FIGURE 4. Allodorylaimus baikalensis sp. n. A: male, entire body; B: female, entire body; C: male anterior body end; D: male head; E: female head; F: vulva region; G, H: male, posterior body end; I: cloaca region; J: female, posterior body end. Scale bars: A, B—100 µm; C, F—50 µm; G, H, J—20 µm; D, E, I—10 µm