Unionicola aculeatella, Tuzovskij, Petr V. & Semenchenko, Ksenia A., 2015

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 : 424-427

Unionicola aculeatella sp.n.

( Figs 20A–E , 21A–E )

Type series. Holotype: 1 male, slide 6908- IBIW, Russia: Samara Province, Stavropol District, National natural Park “Samarskaya Luka”, Gusinoe Lake, depth 0.5–1.0 m, 29.09.1993, leg. P.V. Tuzovskij. Paratypes: 1 male, slide 6599- IBIW, 15.09.1992; 5 males and 4 females (6907-IBIW—female, 7365-IBIW—female, 7366-IBIW—male, 7367-IBIW—two males, 7368-IBIW—male and female, 7340-IBIW—male, 7341-IBIW—two females from the same locality as holotype, 29.09.1993. Additional material: 5 females (slides 9723, 9727; 9728, 9729-IBIW— 2 females, Yaroslavl Province, Nekouz District, Rybinsk reservoir, mouth of the Shumorovka River, near village Pogorelka, depth 0.5–1.0 m, 15.10.2013; 3 females (slides 9730, 9732-IBIW— 2 females), Sunoghka stream, inflow of the Shumorovka River, depth 0.2–0.5 m, 17.10.2013, leg. P.V. Tuzovskij. All males and females were collected free-swimming.

Diagnosis. Adults. Dorsum with two pairs of small unequal platelets; coxal plates III+IV slightly elongated with straight medial margin; P-3 with long lateral and relatively short dorsodistal setae, P-4 with three unequal ventral tubercles, P-5 moderately long with slightly concave ventral margin; anterior genital plates of female large with long subcutaneous accretion; genital plates of male wide, fused to each other by anterior and posterior ends, gonopore narrow; swimming setae on IV-Leg-5 and IV-Leg-6 equal in length, the last with two long, thick setae; claws of legs I thick, hook-like with two unequal clawlets; claws of legs II–IV sickle-shaped.

Description. Both sexes. Dorsum with two pairs of small unequal platelets, anterior platelets relatively large, elongated ( Fig. 20A ); posterior platelets ( Fig. 20B ) oval or circular and considerably smaller than anterior ones. Anterior and posterior coxal groups ( Fig. 20C ) divided by relatively narrow interspace. Apodemes of first coxal group reaching or slightly extending beyond to anterior margin of third coxae. Coxal plates III+IV subquadrate (L/ W ratio 1.0–1.1) with straight medial margin. Sclerites, bearing setae and glandularia Le, larger than sclerites bearing other idiosomal setae. Surface of all coxal plates with reticulations. Genital acetabula relatively small and occupy less than half of area of each plate.

Pedipalps moderately long ( Fig. 21A ): P-2 with four short subequal dorsal setae, P-3 with one long lateral and one relatively short dorsodistal setae, base of lateral seta located near middle of segment, P-4 with large lateral tubercle and two relatively small medial tubercles in distal half of segment, large tubercle and small proximal tubercle bearing thin short seta and one ventrodistal tubercle bearing short peg-like seta, and with one thin dorsoproximal seta; P-5 moderately long with slightly concave ventral margin.

Figure 21B shows the proportion and chaetotaxy of the first leg. 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. 21C ): one on telofemur, three on genu and on tibia; swimming setae on IV-Leg-5 and IV-Leg-6 equal in length, the last with two long, thick setae. Claws of legs I ( Fig. 21D ) thick, hook-like with two unequal clawlets; claws of legs II–IV sickle-shaped with short dorsal clawlet and long ventral one sickle-shaped with short dorsal clawlet and long ventral one ( Fig. 21E ).

Female. Anterior genital plates large, each with long anterior subcutaneous accretion, both medial spines short and nearly subequal; anteromedial seta on posterior plate short, thin ( Fig. 20D ). Posterior plates moderately developed each with 3–4 short, thin setae.

Measurements (n=10). Idiosoma L 680–825; coxae III+IV L 220–235, W 220–230; anterior dorsal platelets L 55–60, W 15–20; posterior dorsal platelets L 18–25, W 12–18; anterior genital plates L 72–85, W 135–140; posterior genital plates L 80–105, W 100–120; pedipalpal segments (P–1–5) L: 20–24, 250–265, 125–130, 240–265, 110–115; leg segments L: I-Leg- 1–6—75 –90, 150–165, 180–190, 280–290, 180–190, 210–220; II-Leg- 1–6—75 –90, 150–170, 180–190, 275–300, 325–340, 320–330; III-Leg- 1–6—75 –90, 110–125, 150–175, 225–235, 250–260, 240–265; IV-Leg-1–6—105–115, 150–175, 210–240, 285–300, 360–375, 330–340.

Male. Genital field ( Fig. 20E ) wider than long, plates fused to each other by anterior and posterior ends, usually with 8–9 thin setae on each side, in additional, one pair of genital setae located on soft integument. Gonopore narrow, twice shorter than width of one genital plate.

Measurements (holotype; in parentheses paratype, n = 2). Idiosoma L 685 (685–750); coxae III+IV L 250 (210–250), W 205 (205–225); anterior dorsal platelets L 48 (48–60), W 18 (15–18); genital field L 195 (180–195), W 210 (215–225); pedipalpal segments (P-1–5) L: 18 (18–20), 114 (105–115), 48 (50–55), 108 (105–115), 54 (50–54); leg segments L: I–Leg– 1–6—62 (60–75), 135 (125–140), 162 (155–175), 250 (235–265), 175 (175–190), 175(175–190); II-Leg- 1–6-62 (60–75), 137 (150–165), 180 (170–190), 262 (240–275), 287 (275–290), 275 (260–290); III-Leg- 1–6-75 (65–75), 105 (105–115), 150 (150–165), 200 (195–205), 210 (205–225), 210 (210–225); IV-Leg- 1–6-87 (85–110), 137 (140–150), 200 (185–215), 250 (250–265), 300 (300–315), 260 (260–275).

Differential diagnosis. The present species is similar to the Unionicola aculeata and U. tricuspis . Unionicola aculeatella sp.n. differs from U. aculeata in the following characters (character states of U. aculeata are indicated in parenthesis). Adults - P-3 with long lateral seta, twice longer than segment, Fig. 21A (short, nearly as long as of segment, Fig. 19A ), P-5 with slightly concave ventral margin (with strongly concave ventral margin); the genital plate of male wide fused to each other by anterior and posterior ends, Fig. 20E (narrow and fused to each other only posterior ends, Fig. 18D ). The anterior genital plates in the female U. tricuspis without anterior subcutaneous accretion each, Fig. 34C ; the gonopore in the male wide, its width nearly equal to width of one genital plate, Fig. 34D ; while in female U. aculeatella sp.n. the anterior genital plates with anterior subcutaneous accretion, Fig. 20D , the gonopore of male narrow, twice shorter than width of one genital plate, Fig. 20E .

Deutonymph. Unknown.

Larva. Unknown.

Etymology. The species epithet “ aculeatella ” is derived from the name of the similar species, Unionicola aculeata .

Habitat. Lakes, reservoirs, running waters.

Hosts. Unknown.

Distribution. Europe ( Russia: Samara and Yaroslavl Provinces).

Figures

FIGURES 20 A – E. Unionicola aculeatella sp. n., adults: A, anterior dorsal plates; B, posterior dorsal plates; C, coxal plates; D – E, genital field; A – D, female; E, male (holotype). Scale bars: A – B = 100 Μm; D – E = 100 Μm.

FIGURES 21 A – E. Unionicola aculeatella sp. n., male: A, pedipalp, lateral view; B, I-Leg- 1 – 6; C, IV-Leg- 4 – 6; D, claw of leg I; E, claw of leg IV. Scale bars: A, D – E = 50 Μm; B = 100 Μm; C = 200 Μm.

FIGURES 19 A – D. Unionicola aculeata, 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.

FIGURES 18 A – D. Unionicola aculeata, adults: A, dorsal plates; B, coxal plates; C – D, genital field; A – C, female; D, male. Scale bars = 100 Μm.

FIGURES 34 A – D. Unionicola tricuspis, adults: A, dorsal plates; B, coxal plates; C – D, genital field; A – C, female; D, male. Scale bars = 100 Μm.