Paratrilobus delicatus ( Shoshin, 1988 ) Andrássy, 2007

Gagarin, Vladimir G. & Naumova, Tatyana V., 2011, Two nematode species of the family Tobrilidae (Enoplida) De Coninck, 1965 from Lake Baikal, Russia, Zootaxa 2815, pp. 59-68 : 64-68

Paratrilobus delicatus ( Shoshin, 1988) Andrássy, 2007

(Figs 3,4; Table 2 )

Material. Ten mature males and 18 mature females. All slides are deposited in the collection of the Limnological Institute, Siberian Branch of the Russian Academy of Sciences (Irkutsk, Russia).

Locality. Gorevoi Utes, Lake Baikal, Siberia, Russia, depth 20 m, 2 km from coast.

Female. Body long, elongate, tapering toward both extremities. Cuticle finely annulated, 1.5 µm thick at midbody. Somatic setae short, scarce. Crystalloids present, bacilliform in shape. Cervical setae absent. Labial region high, offset from the adjacent body; lips well developed. Body diameter at the base of the pharynx 2.2–2.6 times as wide as the labial region diameter. Inner labial sensilla papilliform. Six outer labial sensilla and four cephalic sensilla setiform in shape, long and thin, arranged in a single circle. Outer labial sensilla longer than cephalic sensilla, extending 40–45% of labial region width. Stoma funnel-shaped, slightly curved ventrally. Cheilostom spacious; pharyngostom funnel-shaped with comparatively thick walls. Dorsal pocket and its tooth are absent. Subventral pockets slightly separated from the buccal cavity, overlapping each other, and each with a single tooth. Amphidial fovea cup-shaped, amphidial opening is located at the level of buccal cavity. Pharynx muscular, comparatively long, expanding gradually towards its base. Cardiac glands large, oval, 30–35 µm in diameter. Renette, its canal, ampulla and excretory pore not observed. Reproductive system didelphic, amphidelphic. Ovaries comparatively short, situated to the left of intestine. Oocytes numerous, first in two rows, then as a single row. Vulva a transverse slit, situated slightly anterior to mid-body. Vulval lips sclerotized, not protruding past the body contour. Prevulval glands not observed. Vagina comparatively short, with thick walls. Uterus spacious, containing numerous spindleshaped spermatozoa and one or two intrauterine eggs, measuring 135–146 × 50–55 µm. Rectum 0.9–1.1 times as long as the anal body diameter. Tail slender, comparatively long, gradually narrowing to its terminus. Caudal glands and spinneret well developed.

Males. General morphology is similar to that of females, in structure of cuticle and anterior part of the body. Testes paired, opposed, situated to the left of intestine; anterior testis outstretched, posterior testis reflexed. Vas deferens well developed. Spicules 1.4–1.5 times as long as cloacal body diameter, slender, curved ventrally, with developed capitulum. Gubernaculum short, with distal swelling. Precloacal supplements six in number, strongly protruding, echinate.

Character Male (n = 10) Female (n = 10)

Supplement ampulla slightly flattened, its contents concentrated at ampulla basis. Supplement pad large, armed with small thorns (approximately 40–50 things); cap is comparatively small, with large central thorn. Supplement array 250–331 µm long. Tail slender, long. Caudal setae 8–11 µm long, numerous. Three caudal glands open through short spinneret.

Distribution. Paratrilobus delicatus was described on the basis of three males from Peschanaya Bay, Baikal ( Shoshin, 1988). Females in the original population were not found. This is the second record of this species.

Tables

TABLE 2. Morphometrics of Paratrilobus delicatus (Shoshin, 1988) Andrássy, 2007, (all measurements are given in µm unless otherwise stated, except for the ratios a, b, c, c’, V, spic. cl, and n. eg.).

L	range 2125–2790	mean 2547	range 2333–2794	mean 2551
a b c c’	32–43 4.7–5.8 14.8–20.4 3.1–4.3	39 5.3 17.3 3.7	32–37 4.7–5.4 11.2–15.4 4.5–5.9	34 5.0 13.7 4.9
V,% diam.c.s.	– 26–30	– 28	41.5–47.0 30–34	44.3 32
diam.midb. a.d. o.l.s.	63–67 39–47 11–14	65 41 13	70–81 35–41 11–14	73 38 13
c.s. st.l. st.w.	7–10 26–31 15–17	8 28 16	7–10 27–31 17–19	8 29 18
am.w. dis.am. ph.l. dis.ph.cl. dis.ph. v. dis .v.a.	8–10 8–12 458–588 1717–2165 – –	9 10 464 1930 – –	10–12 10–14 470–558 – 461–698 1080–1440	11 12 510 – 619 1235
Q1 Q2 n.eg.	– – –	– – –	230–338 196–339 0–2	289 277 1
spic. spic.cl gub.l. n.sup. l.sup.r. t.l.	59–62 1.3–1.6 19–21 6 225–331 125–170	60 1.5 20 6 181 153	– – – – – 176–208	– – – – – 187