Unionicola bonzi (Claparède, 1869)

(Figs 22A–D, 23A–D)

Material examined. 1 male, 3 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 single pair of platelets; coxal plates III+IV nearly as long as wide with convex medial margin; P-3 with 2 almost subequal proximal setae; P-4 tapering distally with 3 very small ventral tubercles, P-5 moderately long with strongly concave ventral margin; anterior genital plates of female without anterior subcutaneous projection; 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 all legs subequal, sickle-shaped with short dorsal clawlet and long ventral one.

Description. Both sexes. Dorsum with distinct developed anterior platelets (Fig. 22A), posterior platelets not developed. Anterior and posterior coxal groups (Fig. 22B) divided by rather wide interspace; sclerites, bearing setae and glandularia Le, larger than sclerites bearing other idiosomal setae. Apodemes of first coxal group not reaching to anterior margin of third coxae. Coxal plates III+IV subquadrate (L/W ratio 1.0–1.2) with convex 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. 23A) short and stocky, first 3 segments and proximal portion of tibia expanded dorsoventrally.

P-2 with 5 unequal setae, P-3 with two almost subequal proximal setae; P-4 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 relatively short (P-4/P-5 L 1.8–2.1) with strongly concave ventral margin, both dorsal spines longer than both ventral ones.

Tarsi of all legs slightly thickened distally (Figs 23B–C). 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. 23C): one on telofemur, two on genu and tibia. Swimming setae on leg II shorter than swimming setae on legs III–IV; swimming setae on IV-Leg-5 shorter than IV-Leg-6. Claws of all legs subequal, sickle-shaped with short dorsal clawlet and long ventral one (Fig. 23D).

Female. Anterior genital plates wide without anterior subcutaneous projections, each with two short nearly subequal inner spines and two thin lateral setae (Fig. 22C). Posterior plates more or less triangular, each with short, thin inner seta and 3–5 thin lateral setae.

Measurements (n=2). Idiosoma L 600–650; coxae III+IV L 190–200, W 160–175; anterior dorsal platelets L 35–40, W 15–20; anterior genital plates L 72–85, W 130–145; posterior genital plates L 80–85, W 78–95; pedipalpal segments (P-1–5) L: 18–24, 100–110, 50–60, 100–105, 50–54; leg segments L: I-Leg– 1–6—48 –55, 75–80, 100–105, 135–145, 115–125, 108–120; II-Leg– 1–6—48 –55, 85–90, 105–115, 155–165, 165–175, 140–150; III-Leg– 1–6—48 –55, 70–85, 90–95, 110–120, 130–140, 120–130; IV-Leg– 1–6—85 –90, 90–95, 115–120, 140–150, 180–195, 180–185.

Male. Genital plates (Fig. 22D) fused to each other by posterior ends only, with 8–10 thin setae on each side.

Measurements (n=1). Idiosoma L 650; coxae III+IV L 160–180, W 150–165; anterior dorsal platelets L 30–35, W 8–10; genital field L 220–230, W of one genital plate 40–45; pedipalpal segments (P-1–5) L: 18, 90, 42, 85, 42; leg segments L: I-Leg- 1–6—42, 65, 90,120, 100, 110; II-Leg- 1–6—42, 85, 95, 130, 145, 140; III-Leg- 1–6—48, 65, 78, 105, 120, 120; IV-Leg- 1–6—65, 72, 95, 125, 155, 150.

Deutonymph. See Imamura (1953b), Hevers (1979).

Larva. See Hevers (1980).

Habitat. Lakes, ponds, running waters.

Hosts. Unionidae: Unio pictorum Linnaeus, U. crassus Philipsson, U. tumidus Philipsson and Anodonta cygnea Linnaeus (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). Hevers (1984) described U. imamurai (sibling species of U. bonzi) in Japan based upon some relatively small differences; Wen and his colleagues report Hevers’ species in China (Wen & Zhu, 1999).