Unionicola rezvoi Sokolow 1931

Unionicola rezvoi Sokolow, 1931

(Figs 26A–E, 27A–D)

Material examined. 14 females: Russia, PrimoryTerritory, Khankaysky District, Khanka Lake, Astrakhansky Bay, from mantle cavity of Sinanodonta sp., 16.07.2004, leg. E.I. Barabanschikov.

Diagnosis. Adults. Dorsum with three pairs of small elongated platelets; coxal plates III+IV longer than their width, with convex medial margin; P-3 with two long setae, P-4 slightly tapering distally, with three small tubercles two of which bearing setae, P-5 short, with slightly concave ventral margin; genital field with 5 pairs of genital acetabula, lying on two genital plates in males and four in females; genital plates of male converging posteriorly; 2–3 short thin setae on IV-L-4 and three setae on IV-L-5; claws of legs bifid with subequal clawlets.

Description. Both sexes. Dorsum with three pairs of small elongated platelets (Fig. 26A). Anterior and posterior coxal groups (Fig. 26B) divided by wide interspace, sclerites, bearing setae and glandularia Le, larger than sclerites bearing other idiosomal setae. Apodemes of anterior coxal groups not developed. Coxal plates III+IV elongated (L/W ratio 1.3) with rounded medial margin. Surface of all coxal plates with reticulations.

Pedipalps (Fig. 26C) short and stocky: P-2 with four short setae; P-3 with two long setae; P-4 slightly tapering distally, with three short tubercles two of which bearing seta, middle tubercle longer and more rounded; P-5 short, with slightly concave ventral margin.

First leg (Fig. 27A) shorter than legs II–IV, thick. Legs II–IV long, slender; all segments, except trochanter, cylindrical; with two to three short swimming setae on IV-L-4 and three on IV-L-5 (Fig. 27B). Claws of legs I–IV bifid with nearly equal clawlets (Fig. 27C–D).

Female. Anterior genital plates large, with two unequal acetabula, two short subequal medial spines and two thin, short setae on each side (Fig. 26D). Posterior plates more or less triangular, with a single long, thin inner seta and three more short thin setae.

Measurements (n=2). Idiosoma L 1615–1700; coxae III+IV L 448–462, W 343–370; first pair of dorsal platelets L 70–72, W 22–26; second pair of dorsal platelets L 64–66, W 35–38; third pair of dorsal platelets L 32–33, W 19–20; anterior genital plates L 151–152, W 105–106; posterior genital plates L 174–185, W 105–106; pedipalpal segments (P-1–5) L: 35–40, 132–158, 53–60, 130–132, 65–66; leg segments L: I-Leg-1–6—112–114, 145–191, 218–237, 264–350, 224–264, 210–220; II-Leg-1–6—105–112, 211–231, 343–356, 468–495, 409–442, 297–316; III-Leg-1–6—110–112, 172–191, 224–240, 266–284, 231–250, 211–231; IV-Leg-1–6—171–204, 200–204, 311–320, 356–363, 416–442, 297–310.

Male. Idiosoma L 750–800, short and wide. Genital field in posterior part of idiosoma, heart-shaped (Fig. 26E). Genital plates expanded anteriorly and narrowed distally. Genital acetabula 5 pairs, forming curved lines, middle acetabula usually larger than other (Sokolow 1931, 1940).

Deutonymph. Unknown.

Larva. Unknown.

Habitat. Lakes, rivers.

Hosts. Unionidae: Cristaria plicata (Leach) (Sokolow 1931, 1940) and Sinanodonta sp. (this study). Distribution. Russia (Primory Territory) (Sokolow 1940).