Unionicola rossica Tuzovskij & Semenchenko, 2015, sp.n.

Unionicola rossica sp.n.

(Figs 6A–C, 7A–D)

Syn.: Unionicola dresscheri, Tuzovskij, Biologicheskie Nauki, 1985, 10: 27–33.

Type series. Holotype: female, slide 2819 - IBIW, 3.08.1981, Russia, Magadan Province, Anadyr District, small lakes near settlement Markovo. Paratypes: 13 males, 8 females: from the same locality as holotype, June–September 1978, 1981; 2 males, 3 females: Magadan Province, Tenkinsky District, small lakes near village Agrobasa, June–July 1979. Additional material: 4 females, Samara Province, Stavropol District, National natural Park “Samarskaya Luka”, small lake near village Koltsovo, July 1992, leg. P.V. Tuzovskij. All males and females are collected free-swimming.

Diagnosis. Adults. Dorsal platelets not developed; coxal plates III+IV elongated with straight medial margin; P-3 with two short, thick setae, base of lateral seta located near middle of segment, both setae a little shorter than segment, P-4 with long lateral tubercle, both ventral tubercles small, P-5 moderately long with slightly concave ventral margin; genital plates of male relatively narrow, fused to each other by posterior ends only; anterior plate without front subcutaneous projections, medial setae on all genital plates in female long and subequal; 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. Dorsal platelets not developed. Anterior and posterior coxal groups (Fig. 6A) 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 1.25–1.35) with straight medial margin. Posterior margin of coxal plate oblique, directed posterolaterally. Surface of all coxal plates with reticulations.

Pedipalps (Fig. 7A) moderately long: P-2 with nearly straight ventral margin and three to four proximal setae and single dorsodistal seta, P-3 both setae short, thick, not longer than segment, lateral seta situated near middle of segment, P-4 with long lateral tubercle and two unequal ventral tubercles, bases of lateral tubercle and short anterior ventral tubercle situated near middle of segment; P-5 shorter than P-4 (P-4/P-5 L 1.10–1.35), 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. 7B): three on genu and on tibia. Claws of all legs I (Fig. 7C) hook-like with two unequal clawlets, claws of legs II–IV (Fig. 7D) sickle- shaped with very short dorsal clawlet and long ventral one.

Female. Anterior and posterior genital plates nearly subequal in shape and size (Fig. 6B), anterior plate without front subcutaneous projections, both medial setae long and thick; posterior plates with long anteromedial seta and 3–5 short, thin lateral setae. All acetabula small and occupy less than one half of each genital plate.

Measurements (holotype; in parentheses paratypes, n = 7). Idiosoma L 1060 (895–1220); coxae III+IV L 325 (315–345), W 260 (250–270); anterior genital plates L 85 (70–75), W 80 (90–105); posterior genital plates L 90 (70–95), W 90 (90–105); pedipalpal segments (P-1–5) L: 25 (23–25), 187 (145–215), 90 (90–115), 212 (155–225), 187 (115–205); leg segments L: I-Leg- 1–6—90 (105–115), 225 (285–325), 337 (325–395), 475 (460–540), 375 (350–410), 350 (305–400); II-Leg-1–6—100 (105–115), 250 (290–330), 437 (415–475), 537 (505–570), 575 (570–615), 462 (480–490); III-Leg-1–6—100 (100–115), 200 (250–285), 312 (300–340), 360 (360–400), 425 (405–490), 412 (405–425); IV-Leg-1–6—140 (160–180), 212 (250–285), 362 (355–375), 487 (480–515), 612 (595–655), 525 (495–555).

Male. Genital plates (Fig. 6C) 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=8). Idiosoma L 750–895; coxae III+IV L 250–300, W 190–230; genital field L 160–195, genital plate W 70–85; pedipalpal segments (P-1–5) L: 20–25, 125–190, 70–95, 115–195, 100–170; leg segments L: I-Leg- 1–6—80 –100, 270–305, 275–375, 385–480, 290–390, 270–390; II-Leg- 1–6—80 –100, 250–310, 340–465, 490–565, 545–620, 420–485; III-Leg- 1–6—80 –100, 210–280, 270–310, 335–370, 380–415, 360–410; IV-Leg- 1–6—1120 –165, 225–280, 305–365, 425–505, 520–620, 460–530.

Deutonymph. See Tuzovskij (1985).

Larva. See Tuzovskij (1985).

Differential diagnosis. The water mite Unionicola crassipes var. dresscheri Besseling, 1946 has been is described briefly only on a female (Besseling 1946). Lundblad (1962), Davids (1979) and Smit (1992) stated, that U. dresscheri Besseling, 1946 is synonym to U. crassipes. The present species is similar to the U. crassipes but differs from it in the following characters: dorsal platelets not developed; posterior margin of coxal plate IV (Fig. 6A) oblique, directed posterolaterally; acetabula small (Fig. 6B), and P-3 setae short (Fig. 7A).

Etymology. The species epithet “ rossica ” is named after the country where it was collected (Russia).

Habitat. Lakes.

Hosts. Unknown.

Distribution. Asia, Russia: Magadan Province (Tuzovskij 1985); Europe, Russia: Samara Province.