Arrenurus (Micruracarus) amurensis, 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 : 17-19

Arrenurus (Micruracarus) amurensis sp. n.

( Figs. 35–40 )

Type series. Holotype: male (485-kas– IBSS); Russia, Khabarovsk Territory, Nanaysky District, Amur River basin, former riverbed of the Nura River, 6 km from Gili, N 4948.485'; E 13707.715'; depth up to 1,5 m; detritus, silt, 14.09.2008, leg. K.A. Semenchenko, D.A. Sidorov. Paratypes: 1 male (486-kas– IBSS), same data as holotype.

Description. Male. Idiosoma elongate (ratio length/width 1.25), with concave anterior margin and convex lateral margins, cauda short, distinctly set of from the idiosoma and widest in the middle, with two rounded posterolateral projections ( Fig. 35 ). Setae Fp, Oi and Pi without glandularia, other idiosomal setae associated with glandularia. Distal portion of cauda with pointed petiole and three pairs of setae (Le, Si and Pi); Li placed on platelets fused with other part of dorsal shield, but these platelets may be not separated from lateral dorsal portion.

Setae Fch thicker than setae Fp. Dorsal shield bearing setae Oi, Hi and Sci anteriorly, Li posteriorly; setae and glandularia Sci located on humps ( Fig. 37 ); dorsal furrow incomplete.

Anterolateral corners of coxal plates I and II pointed, reaching to anterior margins of the idiosoma or slightly extending beyond of the anterior idiosoma margin ( Fig. 36 ). Coxal plates I completely fused medially, fragment of suture line between them visible only in the anterior portion. Medial margin of coxal plate III slightly 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 latter extending beyond the lateral idiosoma margin.

Gonopore small and elongate, acetabular plates wide, narrowed laterally and slightly extending onto the dorsal sides of the idiosoma, with numerous acetabula and three or four anterior setae each. Posteromedial cleft with excretory pore in the middle. Setae Hv situated near posterolateral margin of coxal plates II, Pe located between coxal plates IV and acetabular plates, seta Se and Ci located on posterior part of cauda.

Pedipalp normal in size ( Fig. 38 ): P-1 short with a single dorsodistal seta; P-2 thick with concave ventral margin, with two long and 1 short dorsal setae and a patch of numerous short, spine–like mediodistal setae; P-3 relatively short with two subequal setae (internal and external); P-4 relatively long with stout curved and rather long ventrolateral seta, two long, thin dorsodistal setae and one very short medial seta; P-5 with a single solenidion, four thin setae and three spines: proximal spine is pointed, two distal spines with rounded tips.

Telofemur, genu and tibia of legs II–IV with swimming setae; IV– Leg-4 ( Fig. 39 ) without distal projection; 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. 40 ).

Measurements, n=2. L of idiosoma 1010–1045, W 800–833; L of petiole 66–72, W 38–40; L of dorsal shield 790–816, W 540–544; distance between setae Oi–Oi 138–158, distance between setae Hi–Hi 383–442, distance between setae Sci–Sci 120–145, distance between setae Li–Li 116–118; distance between medial margins of coxal plates IV 65 –68; L of basal segment of chelicerae 140–143, L of cheliceral stylet 70–80; L of pedipalpal segments (P-1–5): 42–43, 94–97, 51–56, 97–100, 28–32; L of leg segments: I–Leg- 1–6—90 –92, 125–132, 132–138, 165– 171, 168–178, 180–184; II–Leg- 1–6—92 –94, 132–134, 145–152, 191–204, 200–204, 199–205; III–Leg-1–6— 105–107, 138–145, 140–154, 200–202, 211–218, 194–206; IV–Leg-1–6—152–172, 180–186, 184–191, 218–234, 206–210, 218–224, W of cauda at its base 510–544.

Female. Unknown.

Differential diagnosis. The present species is similar to North American species Arrenurus neocrenellatus Cook, 1976 due to the similar shape of the idiosoma, presence of slight concavities and peg-like petiole on the caudal area. Arrenurus amurensis sp. n. differs from A. neocrenellatus in the following characters (character states of A. neocrenellatus are given in parentheses, data taken from Cook 1976): anterior concavity between eyes is more developed in new species, furrow between dorsal and ventral shields incomplete (complete), petiole situated on dorsal shield (in concavity of caudal area), seta Sci located in the middle of idiosoma (more shifted posteriorly to the caudal area).

Etymology. The species is named after the Amur River, in which basin it was collected.

Habitat. Running waters.

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

Figures

FIGURES 35 – 36. Arrenurus amurensis sp. n., male: 35, idiosoma, dorsal view; 36, idiosoma, ventral view. Scale bar = 100 µm.

FIGURES 37 – 40. Arrenurus amurensis sp. n., male: 37, idiosoma, lateral view; 38, pedipalp; 39, genu, tibia and tarsus of leg IV; 40, claw of leg IV. Scale bars = 100 µm for Fig. 37, 39; 25 µm for Figs. 38, 40.