Unionicola crassipes (O.F. Müller, 1776), O.F. Muller, 1776

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 : 406-408

Unionicola crassipes (O.F. Müller, 1776)

( Figs 1 A –D, 4A–D, 5A–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 two nearly subequal setae, base of lateral seta located distally to middle of segment; P-4 with very long lateral tubercle and relatively short ventrolateral tubercles, P-5 moderately long with slightly concave ventral margin; anterior plates of female without anterior subcutaneous projections, both medial setae long and thick, posterior plates with long, thick medial setae; genital plates of male relatively narrow, fused to each other by posterior ends only; swimming setae on IV-Leg-5 little shorter 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. 4A ), anterior platelets relatively large, elongate; posterior platelets oval or circular and considerably smaller than anterior ones.

Anterior and posterior coxal groups ( Fig. 4B ) divided by relatively wide interspace, sclerites, bearing setae and glandularia Le, much larger than sclerites bearing other idiosomal setae. Apodemes of first coxal group reaching or extending beyond to anterior margin of third coxae. Coxal plates III+IV elongated (L/W ratio 1.25–1.42) with straight medial margin. Surface of all coxal plates with reticulations.

Pedipalps ( Fig. 5A ) moderately long: P-2 with nearly straight ventral margin and four (three proximal and single dorsodistal) short setae, P-3 with one lateral seta located distally to middle of segment and one relatively short dorsodistal seta, P-4 with long lateral tubercle bearing short, thin seta and two relatively small ventral tubercles anterior from them bearing short, thin setae and posterior tubercle bearing short peg-like seta, bases of lateral tubercle and short anterior ventral located near middle of segment; P-5 little shorter than P-4 (P-4/P-5 L 1.15–1.25) 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. 5B ): one 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 shorter than IV-Leg-6. Claws of all legs I ( Fig. 5C ) hook-like with two unequal clawlets, claws of legs II–IV ( Fig. 5D ) sickle-shaped with short dorsal clawlet and long ventral one.

Female. Anterior and posterior genital plates nearly subequal in shape and size ( Fig. 4C ), anterior plate without anterior subcutaneous projections, both medial setae long and thick; posterior plates with long inner setae and 3–5 short lateral setae. All acetabula rather large and occupy about one half of each genital plate.

Measurements (n=10). Idiosoma L 1000–1225; coxae III+IV L 400–465, W 310–360; anterior dorsal platelets L 90–115, W 30–40; anterior genital plates L 75–90, W 100–115; posterior genital plates L 95–105, W 90–105; pedipalpal segments (P-1–5) L: 30–40, 180–220, 95–115, 180–215, 145–180; leg segments L: I-Leg- 1–6—105–125, 305–365, 355–430, 480–595, 360–455, 330–425; II-Leg- 1–6—95 –125, 315–500, 445–515, 560–735, 610–790, 480–650; III-Leg-1–6—105–125, 270–390, 320–450, 370–500, 445–615, 415–540; IV-Leg- 1–6—185–245, 285–370, 350–425, 415–645, 480–640, 455–550.

Male. Genital plates ( Fig. 4D ) relatively narrow, fused to each other by posterior ends, often with subcutaneous accretion and 9–10 thin setae on each side, in additional one pair of genital setae located on soft integument. All acetabula approximately equal in size and occupy less than half of area of each plate.

Measurements (n=8). Idiosoma L 815–1140; coxae III+IV L 310–390, W 225–290; anterior dorsal platelets L 85–100, W 25–40; genital field L 185–225, genital plate W 54–60; pedipalpal segments (P–1–5) L: 20–25, 135–180, 75–100, 120–170, 95–140; leg segments L: I-Leg- 1–6—80 –115, 240–325, 265–400, 365–540, 285–410, 270–350; II-Leg- 1–6—80 –115, 235–385, 350–570, 430–700, 485–785, 390–585; III-Leg- 1–6—80 –100, 225–325, 245–455, 290–310, 350–700, 325–505; IV-Leg-1–6—135–195, 225–345, 285–460, 375–620, 480–800, 425–635.

Deutonymph. See Piersig (1897 –1900), Lundblad (1927), Böttger (1972), Hevers (1979), Tuzovskij (1990).

Larva. See Piersig (1897 –1900), Sparing (1959), Böttger (1972), Wainstein & Tuzovskij (1974), Hevers (1980), Wainstein (1980).

Habitat. Lakes, reservoirs, running waters.

Hosts. Spongillidae : Spongilla biseriata Weltner , Spongilla lacustris Linnaeus , S. fragilis Leidy , Ephydatia fluviatilis (Linnaeus) , E. muelleri (Lieberkühn) , Trochospongilla horrida Weltner (Arndt & Viets 1938, Conroy 1979).

Distribution. Europa, Asia ( Viets 1936, 1956; Sokolow 1940; Lundblad 1968; Viets 1978). Remarks. Length of setae on Р-3 variable: they may be equal or even slightly longer than this segment ( Hevers, 1978a).

Figures

FIGURES 1 A – B. Unionicola crassipes, female: A, dorsal view; B, ventral view. Scale bar = 200 Μm.

FIGURES 4 A – D. Unionicola crassipes, adults: A, dorsal plates; B, coxal plates; C – D, genital field; A – C, female; D, male. Scale bars: A – B = 200 Μm, C = 50 Μm, D = 100 Μm.

FIGURES 5 A – D. Unionicola crassipes, 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.