Ethmolaimus maximus, Gagarin, Vladimir G. & Naumova, Tatyana V., 2012

Gagarin, Vladimir G. & Naumova, Tatyana V., 2012, Paramononchus orientalis sp. n. and Ethmolaimus maximus sp. n. (Nematoda) from Lake Baikal, Russia, Zootaxa 3513, pp. 51-60 : 55-59

Ethmolaimus maximus sp. n.

( Fig. 2 ; Table 2, 3)

Type material. Holotype male, slide reference number 100/46, deposited in the collection of museum of the Institute of Ecology and Evolution, Center for Parasitology, Russian Academy of Sciences (Moscow, Russia).

Paratypes. Ten males and ten females deposited in the collection of the Limnological Institute, Siberian Branch of the Russian Academy of Sciences (Irkutsk, Russia).

Type locality. Bay Bolshie Koty, opposite Dva Brata (Two Brothers) rock, Lake Baikal, Siberia, Russia, sand, depth 3– 4 m. Collected on 10 June 2008.

Etymology. The specific epithet means “very large”, “the largest”.

Description. Male. Body long and comparatively thin, tapering toward both extremities. Cuticle with fine transverse striae and transverse rows of fine homogeneous punctation between transverse striae; lateral differentiation absent. Somatic setae comparatively rare, 11–15 µm long. Head end truncate, corners rounded.

Head continuous with adjacent body, lips amalgamated. Outer labial sensillae and inner labial sensillae in the shape of papillae. Four cephalic sensillae in the shape of thin setae 9–11 µm long, 45–55% of labial region width. Cheilostom armed with 12 cuticularized ribs. Esophastom in the shape of tube with cuticularized walls, separated at two portion. Anterior portion smaller and thicker than posterior portion. Three teeth disposed on the verge of anterior and posterior portions of esophastom. Dorsal tooth slightly larger than both subventral teeth. Stoma equal 1.3–1.4 labial region diameters in length, surrounded by longitudinal musculature. Amphidial fovea semi-spiral, 8–10 µm diameter, located at the region of posterior portion of stoma. Pharynx muscular, with well developed, spherical bulb, measuring 50–60 x 41 –47 µm. Cardia conoid, glandular. Excretory pore located slightly posterior to nerve ring. Renette, renette canal not observed. Diorchic, testes opposed. Anterior testis situated to the left of intestine, posterior testis to the right of intestine. Spicules 1.4–1.5 times as long as the cloacal body diameter, robust, strongly ventrally curved. Gubernaculum also curved, 22–27 µm long. Precloacal supplementary organs cup–like, 13-14 in number. Row of supplements is 225–300 µm long. Tail elongate-conical. Caudal setae 12–16 µm long, arranged in 5–6 subventral and 4–5 subdorsal pairs. Three caudal glands present, opening through comparatively long, conical spinneret.

Т ABLE 2. Morphometrics of Ethmolaimus maximus sp. n. (all measurements are given in µm unless otherwise stated, except

for the rations a, b, c, c’, V, r.an., c.s.r., st.l.l.r., spic.cl., n.sup.)

Character Holotype Paratype males Paratype females male n = 10 n = 10

Female. General morphology is similar to that of males in structure of cuticle and anterior body end. Cuticle with fine transverse striae and transverse rows of fine homogeneous punctation between transverse striae. Somatic setae short and scarce. Head continuous with adjacent body, lips amalgamated. Outer labial sensillae and inner labial sensillae in the shape of papillae. Four cephalic sensillae in the shape of thin setae, as long as 45–55 % of labial region diameter. Cheilostom with 12 cuticularized ribs. Esophastoma in the shape of tube, separated at two portion. Three teeth disposed on the verge both portions. Dorsal tooth slightly larger than both subventral teeth. Stoma surrounded by longitudinal musculature. Amphidial fovea semi-spiral, 6–9 µm diameter, disposed at the region of posterior body portion. Pharynx muscular, with well developed bulb. Rectum 0.9–1.2 times as long as the anal body diameter. Reproductive system didelphic, amphidelphic. Anterior ovary situated to the left of intestine, posterior ovary to the right of intestine. Ovaries reflexed and comparatively short. Oocytes numerous. Vulva a transverse slit, situated slightly anterior to mid-body. Vulval lips not sclerotized and not protruding outside the body contour. Vulval glands present, small. Vagina extending to one-fourth of the corresponding body diameter. Uterus spacious, containing two or five eggs, measuring 42–60 x 35 –46 µm. Tail elongate-conical, with caudal setae 10–12 µm long. Three caudal glands opening through conical spinneret.

caudatus Alekseev & Naumova, 1979, ƤƤ, – – – – – – 3 not found

derisorius Shoshin, 1998 , 3 15 47 1.2 12 40 1.5 Diagnosis. Body 1.71–1.94 mm long in males, 1.65–2.09 mm long in females. Cuticle with fine transverse striae and transverse rows of fine homogeneous punctuation between transverse striae; lateral differentiation absent. Outer labial sensillae and inner labial sensillae in the shape of papillae. Four cephalic sensillae in the shape of thin setae, 45–55 of labial region diameter. Esophastom separated into two portions. Three teeth deposited on the verge of both portions and dorsal tooth slightly longer than subdorsal teeth. Amphidial fovea semi-spiral, disposed at the region of posterior portion of stoma. Pharynx muscular, with well developed bulb. Vulva a transverse slit, situated slightly anterior to mid-body. Vulval gland present. Uterus spacious, containing two or five eggs measuring 42–60 x 35 –46 µm. Spicules comparatively long, strongly ventrally curved. Precloacal supplements 13–14 in number, cup-like. Tail elongate-conical, with caudal setae.

Differential diagnosis. Ethmolaimus maximus sp. n. is the largest species into the genus Ethmolaimus ( Table 3 ). It is closest to E. pratensis , but differs from it in the longer body (L = 1.65–2.09 mm vs L = 0.6–1.2 mm in E. pratensis ), comparatively shorter pharynx (b = 8.0–9.6 vs b = 4.8–7.0 in E. pratensis ), comparatively longer cephalic setae (45–55% of labial region diameter vs 30–35% of labial region diameter in E. pratensis ), longer spicules (52–56 µm long vs 38–48 µm long in E. pratensis ) ( Andrássy, 2005).

Discussion. W. Decraemer & Smal N. (2005) included seven valid species from freshwater bodies in the genus Ethmolaimus de Man, 1880. In electronic database of Texas University (2011) are 12 species of this genus. I. Andrássy (2005) considered 14 valid species: E. bothnicus Jensen, 1994 , E. dahli Gerlach, 1953 , E. derisorius Shoshin, 1998 , E. forely (Hofmaenner, 1913) , E. gracilicaudatus Cobb, 1915 , E. hailuotoensis Torpeenniemi, 1995 , E. intermedius Jensen, 1994 , E. lanatus Shoshin, 1998 , E. multipapillatus, Paramonov, 1926 , E. parapratensis Alekseev, Naumova & Dymina, 1979 , E. pratensis , de Man, 1880, E. pilosus Shoshin, 1998 , E. revaliensis (Schneider, 1906) , E. zullini Eyualem & Coomans, 1996 . But E. foreli and E. gracilicaudatus are synonymised with E. pratensis ( Micoletzky, 1922) ; E. revalensis is synonymised with E. pratensis ( Hirschmann, 1952) ; E. parapratensis is synonymised with E. pratensis ( Platt, 1982) . E. dahli is included in the genus Paraethmolaimus Jensen, 1994 ( Jensen, 1994) . G. Bratschko (1984) is described from high mountain lake in Tyrol ( Austria) specimens of the species Ethmolaimus pratensis , which are comparatively in buccal cavity small dorsal tooth. P. Jensen (1994) erected this morphological morph of E. pratensis in the rang of independent valid species, Ethnolaimus intermedius Jensen, 1994 . We believe that impossible to describe new for science species at one distinctive morphological character (size of dorsal tooth). Therefore E. intermedius reduced in synonym to E. pratensis . Thus, in present time we received 10 valid species in the genus Ethmolaimus (table 3).

Figures

FIGURE 2. Ethmolaimus maximus sp. n., holotype male and paratype female. A: female, entire body; B: male, entire body; C: male head; D: vulval region; E: female tail; F: male, posterior body end. Scale bars: A, B = 150 µm; D – F = 50 µm; C = 20 µm.

Tables

TABLE 3. Morphometrics of valid species of the genus Ethmolaimus de Man, 1880.

Species	L	a	b	c	c’	V
bothnicus Jensen, 1994 , 3	0.64–0.90	20–35	5.2–6.5	7.1–11.5	4.3–4.4	–
caudatus Alekseev & Naumova, 1979, ƤƤ, 3 not found	0.72–0.85	22	5.5	6.0	–	45
derisorius Shoshin, 1998 , 3	0.74–0.80	18–21	6.3–6.7	8.2–8.8	3.5–4.5	–
hailuotoensis Turpeenniemi, 1995 , 3	0.32–0.47	24–36	5.6–7.6	6.2–6.9	6.0	–
lanatus Shoshin, 1998 , 3	0.68–1.18	29–40	5.7–7.3	9.7–11.8	4.0–4.5	–
maximus sp. n. 3	1.71–1.91	27–38	8.2–9.6	10.1–11.7	4.0–5.4	–
multipapillatus Paramonov, 1926 , 3	907	28	8.0	13.5	3.0	–
pilosus Shoshin, 1998 , 3	0.72	19	5.5	8.0	3.8	–
pratensis de Man, 1880, 3	0.62–1.2	16–25	4.8–7.0	8–12	2.5–4.0	–