Unionicola gracilipalpis Viets 1908

Unionicola gracilipalpis (Viets, 1908)

(Figs 10A–D, 11A–D)

Material examined. 1 male, 2 females: Russia, Yaroslavl Province, Nekouz District, small lake near village Pogorelka, July 1975; 2 males, 1 female, Magadan Province, Tenkinsky District, small lakes near village Agrobasa, July 1979; 4 males, 4 females: Magadan Province, Anadyr District, small lakes near settlement Markovo, July–September 1981; 3 females: Samara Province, Stavropol District, National natural Park “Samarskaya Luka”, small lake near village Koltsovo, September 1992, leg. P.V. Tuzovskij. All males and females are collected freeswimming.

Diagnosis. Adults. Dorsum with two pairs of small unequal platelets; coxal plates III+IV elongated with straight medial margin; pedipalp slender, P-3 with relatively short setae (not longer than segment), base of lateral seta located proximally to middle of segment, P-4 with long lateral tubercle, both ventral tubercles small, P-5 long with slightly concave ventral margin; medial setae on all genital plates in female long and nearly subequal; genital plates of male relatively narrow, fused to each other by posterior ends only; swimming setae on IV-Leg-5 shorter than IV-Leg-6; claws of legs I thick, hook-like, claws of legs II–IV thin, sickle-shaped.

Description. Both sexes. Dorsum with two pairs of small unequal platelets (Fig. 10A), anterior platelets relatively large, elongate; posterior platelets very small or not developed. Anterior and posterior coxal groups (Fig. 10B) divided by narrow interspace, sclerites, bearing setae and glandularia Le, much larger than sclerites bearing other idiosomal setae. Apodemes of first coxal group reaching or slightly extending beyond to anterior margin of third coxae. Coxal plates III+IV elongated (L/W ratio 1.3–1.4) with straight medial margin. Surface of all coxal plates with reticulations.

Pedipalps (Fig. 11A) very slender: P-2 with straight or slightly concave ventral margin and three to four proximal setae and single dorsodistal seta; P-3 with relatively long proximolateral and short dorsodistal setae, proximolateral seta not longer than segment; P-4 with long lateral tubercle and two small ventral tubercles, bases of lateral tubercle and short anterior ventral tubercle located near middle of segment; P-5 slightly shorter than P-4 (P- 4/P-5 L1.15–1.25) with slightly concave ventral margin, all simple thin setae and spines short and located distally.

Legs II–IV long, slender. The number of distal swimming setae on legs IV is as follows (Fig. 11B): three on genu and on tibia. Swimming setae on leg II shorter than swimming setae on legs III–IV. Claws of legs I (Fig. 11C) thick, hook-like with two unequal clawlets, claws of legs II–IV (Fig. 11D) thin, sickle-shaped with very short dorsal clawlet and long ventral one.

Female. Anterior and posterior genital plates nearly subequal in shape and size (Fig. 10C); anterior plates without front subcutaneous projections, both medial setae long unequal on each plate; posterior plates with long anteromedial seta and 3–5 short, thin setae. All acetabula moderately in size and occupy less than one half of area of each genital plate.

Measurements (n=10). Idiosoma L 850–1240; coxae III+IV L 410–560, W 310–465; anterior genital plates L 80–100, W 95–115; pedipalpal segments (P-1–5) L: 30–50, 260–305, 120–165, 275–335, 235–270; leg segments L: I-Leg-1–6—110–135, 350–410, 470–560, 640–775, 535–600, 385–410; II-Leg-1–6—105–125, 385–410, 530–660, 625–760, 690–850, 530–640; III-Leg- 1–6—95 –135, 285–345, 380–435, 430–500, 485–600, 440–525; IV-Leg-1–6—160–215, 315–340, 430–525, 570–685, 715–950, 545–735.

Male. Acetabular plates (Fig. 10D) relatively narrow, fused to each other by posterior ends, 8–10 thin unequal setae on each side, in additional, one pair of genital setae located on soft integument. All acetabula very small subequal and occupy less than half of area of each plate.

Measurements (n=7). Idiosoma L 73–900; coxae III+IV L 350–400, W 275–285; genital field L 190–225, genital plate W 73–80; pedipalpal segments (P–1–5) L: 24–30, 200–230, 85–125, 210–255, 170–180; leg segments L: I-Leg- 1–6—95 –110, 285–325, 365–410, 505–610, 445–515, 340–410; II-Leg- 1–6—90 –110, 325–350, 490–575, 570–685, 650–850, 420–700; III-Leg- 1–6—90 –110, 250–285, 330–375, 365–435, 445–500, 415–500; IV-Leg-1–6—135–160, 260–285, 385–460, 510–625, 650–760, 545–650.

Deutonymph. See Tuzovskij (1990).

Larva. See Prasad & Cook (1972), Hevers (1980).

Habitat. Lakes.

Hosts. Spongillidae (Hevers 1980).

Distribution. Europe (Viets 1936, 1956; Sokolow 1940; Lundblad 1968; Viets 1978), Asian Russia (Tuzovskij 1990; Semenchenko 2010; Semenchenko et al. 2010; Semenchenko & Matafonov 2014), North America (Prasad & Cook 1972). North American specimens include U. gracilipalpis tenuis (Lundblad, 1935) (Cook, 1980).