Unionicola aculeata (Koenike, 1890)

Tuzovskij, Petr V. & Semenchenko, Ksenia A., 2015, Water mites of the genus Unionicola Haldeman, 1842 (Acari, Hydrachnidia, Unionicolidae) in Russia, Zootaxa 3919 (3), pp. 401-456 : 422-424

Unionicola aculeata (Koenike, 1890)

( Figs 18A–D , 19A–D )

Material examined. 8 males, 7 females: Russia, Samara Province, Stavropol District, National natural Park “Samarskaya Luka”, Gusinoe Lake, July–September 1992. 7 males, 9 females: Yaroslavl Province, Nekouz District, Rybinsk reservoir near settlement Borok, September–October 2003, 2013, leg. P.V. Tuzovskij. All males and females are collected free-swimming.

Diagnosis. Adults. Dorsum with two pairs of small unequal platelets; coxal plates III+IV elongated with straight medial margin; P-3 with long lateroproximal seta and relatively short dorsodistal seta; P-4 tapering distally, ventrolateral tubercles located distally to middle of segment, P-5 moderately long with strongly concave ventral margin; anterior genital plates of female each with long subcutaneous accretion; genital plates of male relatively narrow and fused to each other by posterior ends only; swimming setae on IV-Leg-5 slightly longer 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. 18A ), anterior platelets relatively large, elongate; posterior platelets oval or circular and considerably smaller than anterior ones. Anterior and posterior coxal groups ( Fig.18B ) divided by relatively narrow interspace, sclerites, bearing setae and glandularia Le, larger than sclerites bearing other idiosomal setae. Apodemes of first coxal group rather long and well extending beyond to anterior margin of third coxae. Coxal plates III+IV elongated (L/W ratio 1.2–1.3) with straight medial margin. Surface of all coxal plates with reticulations. Genital acetabula relatively small and occupy less than half of area of each plate.

Pedipalps ( Fig. 19A ) short and stocky, first three segments and proximal portion of tibia expanded dorsoventrally, P-2 with four (three proximal and single dorsodistal) short setae, P-3 with one long lateroproximal seta and one relatively short dorsodistal seta; P-4 tapering distally, with two unequal ventrolateral tubercles distally to middle of segment and each bearing thin short seta and one ventrodistal tubercle bearing short peg-like seta, and with one thin dorsoproximal seta; P-5 relatively short (P-4/P-5 L 1.8–2.0) with strongly concave ventral margin.

Legs II–IV long, slender; all segments, except trochanter, cylindrical and with swimming setae. The number of distal swimming setae on legs IV is as follows ( Fig. 19B ): two on telofemur, three on genu and on tibia. Swimming setae on leg II shorter than swimming setae on legs III–IV; swimming setae on IV-Leg-5 little longer than IV-Leg- 6, the last with three long, thick subequal ventral setae. Claws of legs I ( Fig. 19C ) thick, hook-like with two unequal clawlets; claws of legs II–IV sickle-shaped with short dorsal clawlet and long ventral one ( Fig. 19D ).

Female. Anterior genital plates wide each with long anterior subcutaneous accretion, posterior inner spine thicker than anterior inner on each side ( Fig. 18C ). Posterior plates more or less triangular, each with short, thin inner seta and 7–9 short, thin lateral setae.

Measurements (n=9). Idiosoma L 900–1140; coxae III+IV L 325–365, W 250–270; anterior dorsal platelets L 75–90, W 25–30; posterior dorsal platelets L 18–25, W 12–18; anterior genital plates L 75–90, W 125–150; posterior genital plates L 100–115, W 110–140; pedipalpal segments (P–1–5) L: 24–33, 180–190, 90–100, 160–165, 80–90; leg segments L: I-Leg- 1–6—90 –105, 225–260, 240–260, 350–370, 220–245, 225–240; II-Leg- 1–6—80 –100, 250–260, 265–285, 355–390, 365–385, 285–325; III-Leg- 1–6—90 –100, 200–215, 210–220, 210–220, 260–270, 265–285, 255–265; IV-Leg-1–6—145–170, 200–230, 265–280, 315–330, 390–410, 350–360.

Male. Genital plates ( Fig. 18D ) relatively narrow, fused to each other by posterior ends only, with 10–13 thin setae on each side.

Measurements (n=5). Idiosoma L 815–940; coxae III+IV L 305–325, W 200–225; anterior dorsal platelets L 65–75, W 25–30; genital field L 220–230, genital plate W 54–60; pedipalpal segments (P-1–5) L: 16–24, 135–145, 55–82, 130–150, 70–82; leg segments L: I-Leg- 1–6—80 –100, 225–240, 240–250, 325–345, 220–230, 210–230; II- Leg- 1–6—80 –90, 220–250, 270–285, 375–385, 350–370, 290–305; III-Leg- 1–6—80 –90, 175–205, 200–270, 250–260, 250–270, 240–260; IV-Leg-1–6—130–140, 185–230, 250–260, 300–320, 355–375, 305–335.

Deutonymph. See Hevers (1979).

Larva. See Hevers (1980), Wainstein (1980).

Habitat. Lakes, reservoirs, ponds, running waters.

Hosts. Unionidae and Viviparidae . Very numerous hosts on different continents ( Viets & Plate 1954; Hevers 1980; Böttger 1972; Wen & Zhu 1999; Edwards & Vidrine 2013).

Distribution. Europe, Asia, North America ( Viets 1936, 1956; Sokolow 1940; Lundblad 1968; Viets 1978; Edwards & Vidrine 2013).

Figures

FIGURES 18 A – D. Unionicola aculeata, adults: A, dorsal plates; B, coxal plates; C – D, genital field; A – C, female; D, male. Scale bars = 100 Μm.

FIGURES 19 A – D. Unionicola aculeata, female: A, pedipalp, lateral view; B, IV-Leg 4 – 6; C, claw of leg I; D, claw of leg IV. Scale bars: A = 100 Μm, B = 200 Μm, C – D = 50 Μm.