Unionicola arcuata (Wolcott, 1898)

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 : 451-453

Unionicola arcuata (Wolcott, 1898)

( Figs 43A–D , 44A–B )

Material examined. 2 males, 3 females: Russia, Primory Territory, Khankaysky District, Khanka Lake, region of Luzanovaya hill, 10.08.2012, from mantle cavity of Sinanodonta schrencki Moskvicheva , leg. S.G. Surmach; 3 males, 3 females: Russia, Primory Territory, Nadezhdensky District, former riverbed of Ananevka, 12.10.2005, from mantle cavity of Cristaria sp., leg. M.B. Shedko; 1 female, Russia, Primory Territory, Oktyabrsky District, former riverbed lake near station Razdolnaya, 15.09.2010, from mantle cavity of Sinanodonta primorjensis Bogatov & Zatravkin , leg. V.V. Bogatov.

Diagnosis. Adults. Dorsum without any platelets; coxal plates III+IV subquadrate with convex medial margin; P-3 with long proximal and short distal setae, P-4 slightly tapering distally, with three small unequal tubercles, P-5 with three unequal distal spines; genital acetabula 16–35 pairs in females and 21–34 pairs in males; genital field of female with two wide plates; genital plates of male wide, fused to each other posteriorly; legs without swimming setae, IV-Leg-6 curved; leg claws stout sickle-shaped with short dorsal clawlet and long ventral one.

Description. Both sexes. Dorsum without any platelets. Anterior and posterior coxal groups ( Figs 43A , 44A ) divided by wide interspace, sclerites, bearing setae and glandularia Le, not larger than sclerites bearing other idiosomal setae. Apodemes of first coxal groups short and truncated. Coxal plates III+IV subquadrate (L/W ratio 0.94–1.28) with rounded medial margin. Surface of all coxal plates punctated.

Pedipalps ( Fig. 43C ) short and stocky: P-2 with five setae; P-3 with long proximal and short distal setae; P-4 slightly tapering distally, with three tubercles two of which bearing seta, lateral tubercle longer than other tubercles; P-5 short, with three unequal distal spines.

Legs long and slender, last segments more slender, with widened distal dorsal setae, IV-Leg-6 curved ( Fig. 43D ); all segments, except trochanter, cylindrical; legs II–III with 2–3 short thin setae. Claws of all legs thick sickle-shaped with short dorsal clawlet and long ventral one ( Figs 43E, F ).

Male. Genital plates of male wide, fused to each other posteriorly, with 21–34 pairs acetabula and 9–10 short, thin setae; two acetabula on each plate enlarged ( Fig. 43B ).

Measurements (n=2). Idiosoma L 1275–1290; coxae III+IV L 408–541, W 376–425; genital plates L 224–237, W 138–151; pedipalpal segments (P-1–5) L: 27–34, 148–152, 72–82, 124–138, 70–77; leg segments L: I-Leg- 1–6—92 –104, 165–166, 172–184, 238–264, 231–250, 158–172; II-Leg- 1–6—92 –100, 165–191, 244–303, 343–363, 336–365, 237–244; III-Leg-1–6—105–106, 185–191, 230–231, 270–284, 323–342, 283–284; IV-Leg- 1–6—172–195, 198–231, 277–310, 320–366, 449–495, 403–442.

Female. Genital field with two wide acetabular plates, with 16–35 acetabula and 9–11 thin unequal setae; three to four acetabula on each side enlarged ( Fig. 44B ).

Measurements (n=2). Idiosoma L 1224–1258; coxae III+IV L 415–595, W 442–460; genital plates L 231–237, W 165–198; pedipalpal segments (P-1–5) L: 28–36, 138–140, 79–85, 131–145, 72–73; leg segments L: I-Leg- 1–6—92 –105, 172–178, 173–191, 251–270, 231–264, 165–178; II-Leg- 1–6—92 –99, 198–204, 271–290, 356–382, 373–402, 242–264; III-Leg-1–6—112–113, 190–198, 244–257, 280–303, 344–370, 296–297; IV-Leg- 1–6—198–205, 199–230, 290–327, 363–396, 488–525, 448–455.

Larva. Unknown.

Deutonymph. See Imamura 1953b.

Habitat. Lakes, rivers, brooks.

Hosts. Unionidae . Very numerous hosts species on different countries and continents ( Imamura 1953a; Wen & Zhu 1999; Wu et al. 2012; Edwards & Vidrine 2013). Hosts in Russia: Sinanodonta schrencki , S. primorjensis , Cristaria sp. (this study).

Distribution. Russia (Primory Territory) (this study), China ( Wen & Zhu 1999), North America ( Vidrine 1986; Edwards & Vidrine 2013). This species is reported from Russia for the first time.

Remaks. Wu et al. (2012) indicated with DNA analyses that this species includes a number of host-associated if not geographical associated cryptic species. M.F. Vidrine (1986) indicated that at least 3 host-associated species were discernable among North American populations, but he did not separate these species at that time. Additional researches may explicate the species-level taxonomy of these mites.

Figures

FIGURES 43 A – F. Unionicola arcuata, adults: A, coxal plates, B, genital field; C, pedipalp, lateral view; D, IV-Leg- 1 – 6; E, claw of leg I; F, claw of leg IV; A – B, D – F, male; C, female. Scale bars: A – D = 100 Μm, E – F = 25 Μm.

FIGURES 44 A – B. Unionicola arcuata, female: A, coxal plates; B, genital field. Scale bars = 100 Μm.