Arrenurus (Arrenurus) mucropetiolatus, Tuzovskij, Petr V. & Semenchenko, Ksenia A., 2011

Tuzovskij, Petr V. & Semenchenko, Ksenia A., 2011, New water mite species of the genus Arrenurus Dugs, 1834 (Acariformes, Hydrachnidia, Arrenuridae) from the Far East of Russia, Zootaxa 3037, pp. 1-20 : 2-4

Arrenurus (Arrenurus) mucropetiolatus sp. n.

( Figs. 1–9 )

Type series. Holotype: male (9647– IBIW); Russia, Primory Territory, Anuchinsky District, Arsenyevka River basin, Konny brook (left inflow of Arsenyevka River), N 4341.093'; E 13359.927'; depth 10–30 cm; substrates: pebbles, medium-grained sand, detritus, 14.09.2008, leg. K.A. Semenchenko, D.A. Sidorov. Paratypes: 1 male (9646– IBIW) and 1 female (9647a– IBIW), same data as holotype; 1 female (481-kas– IBSS), Russia, Primory Territory, Kavalerovsky District, Sea of Japan basin, small pond, connected with Vysokogorskaya River, N 4418.464'; E 13509.962'; depth 30–60 cm; substrates: stones, detritus, 25.09.2008, leg. K.A. Semenchenko, D.A. Sidorov.

Description. Male. Idiosoma ( Fig. 1 ) elongate (ratio length/width 1.4), semicircular in anterior half and tapering distally; cauda moderately long and indistinctly set off from the remainder of the idiosoma. Setae Fp, Oi and Pi without glandularia, other idiosomal setae associated with glandularia. Setae Fch thicker than setae Fp. Dorsal shield elongate, bearing three pairs of setae (Oi, Hi and Sci) in anterior half; distance between setae Oi–Oi and Sci– Sci approximately subequal and less than distance between setae Hi–Hi. Distal portion of cauda bearing petiole and four pairs of setae (Li, Le, Si and Pi); Li short and placed on two relatively large separate humps, Le and Si long, Pi strong curved and shorter than Si. Petiole relatively short, without hyaline membrane, with parallel lateral margin and more or less pointed distally ( Figs. 2–3 ).

Anterolateral corners of coxal plates I and II pointed, reaching only to anterior margins of the idiosoma ( Fig. 4 ). Coxal plates I completely fused to each other medially, fragment of suture line between them visible only in the anterior portion. Medial margin of coxal plate III shorter than medial margin of coxal plate IV, anterolateral corner of coxal plate III and lateral projection of coxal plate IV with rounded tips, the last extending beyond the idiosoma proper. Gonopore small and narrow, acetabular plates wide and reaching lateral margins of the idiosoma, with numerous acetabula and three anterior setae each. Excretory pore open on small tubercle beyond the petiole. Setae Hv situated near posterolateral margin of coxal plates II, Pe located anteriorly of the acetabular plates, seta and glandularia Se well separated and located behind these plates, Ci in posterolateral corners of the cauda.

Pedipalp compact ( Fig. 5 ): P-1 short with a single dorsodistal seta; P-2 thick with concave ventral margin, with five approximately subequal long dorsodistal setae and a patch of numerous short, spine–like mediodistal setae; P- 3 relatively short with two approximately subequal setae (internal and external); P-4 stocky with a stout, curved and rather long antagonistic bristle, two long, thin dorsodistal setae and two very short distal setae; P-5 with a single solenidion, four thin setae and three spines: proximal spine is pointed, two distal spines with rounded tips.

Tibia of legs II, genu and tibia of legs III and IV with swimming setae; IV–Leg-4 ( Fig. 6 ) with distal projection, bearing four setae, this projection relatively short and moderately extending beyond insertion of the fifth segment; IV–Leg-5 slightly longer than IV–Leg-4, IV–Leg-5 and IV–Leg-6 approximately equal in length; claws of fourth legs with two nearly subequal denticles, claw lamella with convex ventral margin ( Fig. 7 ).

Measurements, n=2. L of idiosoma (except petiole) 760–810, W 500–550; L of petiole 35–45, width 24–27; L of dorsal shield 625–650, width 370–380; distance between setae Oi–Oi 125–150, distance between setae Hi–Hi 260–275, distance between setae Sci–Sci 150–165, distance between setae Li–Li 50–60; distance between medial margins of coxal plates IV 30–35; L of basal segment of chelicerae 78–85, L of cheliceral stylet 54–60; L of pedipalpal segments (P-1–5): 34–36, 63–72, 35–45, 63–75, 24–30; length of leg segments: I–Leg- 1–6—60 –65, 75–80, 100–115, 120–130, 120–140, 150–175; II–Leg- 1–6—60 –65, 72–85, 115–120, 144–150, 140–150, 165–195; III– Leg- 1–6—65 –72, 105–115, 120–155, 150–170, 160–170, 170–180; IV–Leg- 1–6—105–115, 105–120, 132–145, 135–150, 150–160, 150–170, L of distal projection of IV–Leg-4 45–48.

Female. Idiosoma oval, wide (ratio L/ W 1.15 –1.2) with slightly convex frontal and caudal margins, without dorsal humps. Dorsal and ventral shields present. Dorsal shield large, narrowed anteriorly and bearing setae Oi, Hi, Sci and Li; glandularia Li open on small tubercles ( Fig. 8 ). Furrow between ventral and dorsal shields complete. Anterolateral corners of coxal plates I pointed, reaching but not extending beyond the idiosoma proper ( Fig. 9 ). Posterior coxal groups well separated, medial margin of coxal plates III shorter than medial margin of coxal plates IV, lateral projection of coxal plate IV only reaching lateral margin of the idiosoma. Gonopore and acetabular plates well separated; gonopore large, surrounded by narrow ring, genital flaps elongate (ratio L/ W 1.8 –2.1) and without patches; width of genital flap less than distance between medial margins of coxal plates IV. Acetabular plate relatively small, nearly rounded, bearing numerous small acetabula and two short, fine (anteromedial and posterior) setae, wider than distance between posterior coxal groups and placed slightly posterior to middle of the idiosoma. Setae and glandularia Se well separate, Pi shorter than Ci; excretory pore open between glandularia Ci. Pedipalps as in male but femur with 3 dorsodistal setae.

Measurements, n=2. L of idiosoma 935–1003, W 810–833; L of dorsal shield 670–710, W 595–635; distance between setae Oi–Oi 172–210, distance between setae Hi–Hi 363–425, distance between setae Sci–Sci 297–360, distance between setae Li–Li 200–250; distance between medial margins of coxal plates IV 80 –90; L of genital flaps 135–158, width 73–75; L of genital plates 130–148, width 135–185; L of basal segment of chelicerae 110– 135, L of cheliceral stylet 55–75; L of pedipalpal segments (P-1–5): 30–38, 67–73, 37–46, 80–82, 30–32; L of leg segments: I–Leg- 1–6—50 –80, 85–112, 100–132, 125–145, 130–145, 125–152; II–Leg- 1–6—50 –72, 85–112, 100– 140, 150–178, 155–178, 155–180; III–Leg- 1–6—55 –79, 90–105, 100–132, 160–178, 180–191, 160–185; IV–Leg- 1–6—132–150, 110–165, 145–178, 175–204, 185–211, 160–198.

Differential diagnosis. Arrenurus mucropetiolatus sp. n. is similar to the European species Arrenurus subarcticus Lundblad, 1917 . The male of the new species differs in the cauda without posterolateral projections, seta and glandularia Li located far beyond from distal end of the cauda, the petiole with more or less pointed distal end, ligulate process not developed; in contrast, the cauda is with distinct small posterolateral projections, seta and glandularia Li located caudally, the petiole with straight distal end, ligulate process wide and placed in distal half of the petiole in the male A. subarcticus ( Lundblad 1917, 1930, 1962).

Etymology. The species is named for the pointed distal end of the petiole.

Habitat. Running and standing waters.

Distribution. Asia ( Russia: Far East, Primory Territory).

Figures

FIGURES 1 – 4. Arrenurus mucropetiolatus sp. n., male: 1, idiosoma, dorsal view; 2 – 3, petiole, dorsal view; 4, idiosoma, ventral view. Scale bars = 100 µm for Figs. 1, 4; 50 µm for Figs. 2 – 3.

FIGURES 5 – 7. Arrenurus mucropetiolatus sp. n., male: 5, pedipalp; 6, genu, tibia and tarsus of leg IV; 7, claw of leg IV. Scale bars = 100 µm for Fig. 6; 50 µm for Figs. 5, 7.

FIGURES 8 – 9. Arrenurus mucropetiolatus sp. n., female: 8, idiosoma, dorsal view; 9, idiosoma, ventral view. Scale bar = 100 µm.