Unionicola intermedia (Koenike, 1882)

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 : 403-406

Unionicola intermedia (Koenike, 1882)

( Figs 2A–D , 3A–D )

Material examined. 1 male, 4 females (free-swimming): Ukraine, Odessa Province, Danube River near settlement Vilkovo, 0 3.07.2011, leg. L.N. Yanovich, T.V. Shevchuk.

Diagnosis. Adults. Dorsum with two pairs of unequal platelets; coxal plates III+IV weakly elongated with straight medial margin; P-3 with two long and almost subequal setae (proximal and distal), P-4 tapering distally, with three very small ventral tubercles, P-5 moderately long with strongly concave ventral margin; anterior genital plates of female with small anterior subcutaneous extension and two short subequal medial spines, each posterior genital plates with long, thin anteromedial seta; genital plates of male relatively narrow, not fused to each other; IV- Legs with sexual dimorphism, swimming setae on IV-Leg-5 shorter than IV-Leg-6; claws of all legs subequal, with two long subequal clawlets.

Description. Both sexes. Dorsum with distinct developed anterior and posterior platelets but anterior platelets larger than posterior ones ( Fig. 2A ). Apodemes of first coxal group reaching or slightly extending to anterior margin of third coxae ( Fig. 2B ). Coxal plates III+IV subquadrate (L/W ratio 1.1–1.3) with straight medial margin. Surface of all coxal plates with reticulations. Sclerites, bearing glandularia Le, small; setae and glandularia Le usually separated. Genital acetabula relatively small and occupy less than half of area of each plate.

Pedipalps ( Fig. 3A ) moderately long, first three segments expanded dorsoventrally; P-2 with four unequal setae, P-3 with two long subequal setae (proximal and distal); P-4 slightly tapering distally, with two very small ventral tubercles distally to middle of segment and each bearing thin, short seta and one small ventrodistal tubercle bearing short peg-like seta; P-5 moderately long with strongly concave ventral margin, both dorsal spines longer than both ventral ones.

Tarsi of all legs thickened distally ( Figs 3B–C ). Legs II–IV long, slender; all segments, except trochanter and tarsus, cylindrical and with swimming setae. Swimming setae on leg II shorter than swimming setae on legs III–IV; swimming setae on IV-Leg-5 much shorter than IV-Leg-6. Claws of all legs bifid, with two subequal clawlets ( Fig. 3D ).

Female. Anterior genital plates wide each with small anterior subcutaneous extension, each with two short subequal medial spines and two thin setae ( Fig. 2C ). Posterior plates more or less triangular, each with long, thin anteromedial seta, and 4–5 short, thin setae, acetabula rather large and occupy about one half of each posterior plate. IV-Leg-4–5 with thin ventral setae ( Fig. 3B ).

Measurements (n=2). Idiosoma L 770–940; coxae III+IV L 270–300, W 235–245; anterior dorsal platelets L 60–75, W 42–55; anterior genital plates L 75–90, W 135–150; posterior genital plates L 75–90, W 90–105; pedipalpal segments (P-1–5) L: 24–30, 120–125, 60–66, 125–135, 72–78; leg segments L: I-Leg- 1–6—75 –90, 125–140, 150–175, 235–250, 195–205, 195–205; II-Leg- 1–6—75 –90, 150–165, 210–225, 325–340, 285–300, 250–265; III-Leg- 1–6—85 –95, 110–125, 150–165, 200–215, 175–190, 195–205; IV-Leg-1–6—145–155, 135–150, 210–225, 260–275, 325–340, 250–265.

Male. Genital plates ( Fig. 2D ) narrow not fused to each other, with 8–10 thin setae on each side. All acetabula approximately equal in size. IV-Leg-4–5 with thick ventral setae ( Fig. 3C ).

Measurements (n=1). Idiosoma L 625; coxae III+IV L 260, W 200; anterior dorsal platelets L 65–72, W 30–36; genital field L 220–230, W of one genital plate 135–65; pedipalpal segments (P–1–5) L: 25, 90, 60, 100, 60; leg segments L: I-Leg- 1–6—75, 125, 150, 210, 175, 185; Leg- 1–6—75, 160, 225, 325, 285, 210; III-Leg- 1–6—75, 100, 150, 175, 150, 165; IV-Leg-1–6—125, 125, 225, 200, 250, 200.

Deutonymph. See Piersig (1897 –1900), Lundblad (1927), Hevers (1979).

Larva. See Hevers (1980).

Habitat. Lakes, ponds, running waters.

Hosts. Unionidae : Unio tumidus Philipsson , Anodonta anatina Linnaeus , A. cygnea Linnaeus , Pseudanodonta complanata (Rossmaessler) ( Viets & Plate 1954, Hevers 1980).

Distribution. Widely distributed in Europe including the European part of Russia ( Viets 1936, 1956; Sokolow 1940; Lundblad 1968; Viets 1978).

Remarks. The sexual dimorphism of U. intermedia is illustrated in detail in Hevers (1978a). The function of the sexual dimorphism and the sexual biology is described in Hevers (1978b).

Figures

FIGURES 2 A – D. Unionicola intermedia, adults: A, dorsal plates; B, coxal plates; C – D, genital field; A – C, female; D, male. Scale bars: A – B = 200 Μm, C – D = 100 Μm.

FIGURES 3 A – D. Unionicola intermedia, adults: A, pedipalp, lateral view; B – C, IV-Leg- 4 – 6; D, claw of leg IV; A – B, D, female; C, male. Scale bars: A, D = 50 Μm, B – C = 200 Μm.