Arrenurus (Arrenurus) crenatiformis, 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 : 5-8

Arrenurus (Arrenurus) crenatiformis sp. n.

( Figs. 10–16 )

Type series. Holotype: male (9645– IBIW); Russia, Amurskaya Area, Seryshevsky District, Zeya River basin, Tom’ River, 2 km from Vasilyevka, N 5054.149'; E 12838.303'; depth 50 cm; substrates: medium-grained sand, detritus, 20.07.2005, leg. K.A. Semenchenko, D.A. Sidorov. Paratypes: 1 male (126-kas– IBSS) and 1 female (482- kas– IBSS), Russia, Shimanovsky District, Zeya River basin, inflow of the Belava River, N 5205.026'; E 12741.638'; depth 50–70 cm; substrates: stones, medium-grained sand, detritus, silt, 21.07.2005, leg. K.A. Semenchenko, D.A. Sidorov.

Description. Male. Idiosoma ( Fig. 10 ) wide (ratio L/ W 1.1), with concave anterior margin and convex lateral margins, cauda very short and distinctly set of from the remainder of the idiosoma; pygal lobes relatively short and directed more or less posterolaterally. Dorsal shield large truncate anteriorly, bearing setae Oi and Hi in anterior half, setae and glandularia Sci located on somewhat rounded humps distally to the middle of the shield, bases of setae Li close together medially near posterior end of the idiosoma, Le near distal end of pygal lobes. Dorsal furrow passing onto sides of idiosoma at base of pygal lobes. Setae Fp, Oi and Pi without glandularia, other idiosomal setae associated with glandularia. Distance between setae Oi–Oi nearly three times shorter than distance between setae Hi–Hi. Petiole large and elongate, narrowed anteriorly, widest near middle, posterior margin of petiole concave, ligulate process pointed, narrow and located in anterior half of the petiole; hyaline membrane not developed; Pi longer than petiole, Si considerably longer than Pi.

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. 11 ). Coxal plates I fused to each other medially, suture line present only in theirs anterior half. Medial margin of coxal plate III shorter than medial margin of coxal plate IV, anterolateral corner of coxal plates III and lateral projection of coxal plates IV with rounded tips, the latter extending beyond the lateral idiosoma margin. Gonopore small and elongate; acetabular plates wide and reaching lateral margins of the idiosoma, with rather numerous acetabula and three fine setae near anterior margin. Excretory pore open on small tubercle in the integument between gonopore and base of cauda. Setae Hv situated near posterolateral margin of coxal plates II, Pe located beyond acetabular plates, Ci located medially to pygal lobes, seta and glandularia Se well separated and located on pygal lobes.

Pedipalp stocky ( Fig. 12 ): P-1 short with a single dorsodistal seta; P-2 thick with straight ventral margin, with two dorsodistal and two ventrodistal setae and one mediodistal seta, all these setae approximately equal in length; P-3 relatively short, with two (internal and external) approximately subequal setae; P-4 relatively long, with stout and rather long antagonistic bristle, two thin dorsodistal setae and two short distal setae; P-5 with a single solenidion, four thin setae and three unequal spines.

Tibia of legs II, genu and tibia of legs III and IV with swimming setae. Genu of leg IV ( Fig. 13 ) with long and straight distal projection, bearing five relatively short setae; IV–Leg-4 longer than IV–Leg-5; leg claws ( Fig. 14 ) with two unequal pointed denticles, claw shorter than clawlet, claw lamella with convex ventral margin.

Measurements, n=2. L of idiosoma (except petiole) 1035–1105, W 925–935; L of petiole 237–250, W 145– 150; L of dorsal shield 750–800, W 630–660; distance between setae Oi–Oi 160–165, distance between setae Hi– Hi 488–510, distance between setae Sci–Sci 218–285, distance between setae Li–Li 36–50; distance between medial margins of coxal plates IV 37 –40; L of basal segment of chelicerae 140–160, L of cheliceral stylet 70–80; L of pedipalpal segments (P-1–5): 42–43, 92–105, 75–84, 118–119, 40–42; L of leg segments: I–Leg- 1–6—85 –92, 140–150, 165–175, 204–210, 185–198, 231–235; II–Leg- 1–6—70 –85, 140–160, 185–191, 230–250, 230–235, 257–260; III–Leg-1–6—100–105, 150–167, 175–178, 225–237, 200–239, 210–224; IV–Leg-1–6—158–175, 250– 264, 255–270, 284–390, 178–185, 213–230, L of distal projection of IV–Leg-4 112–125.

Female. Idiosoma wide (ratio L/ W 1.08 –1.18), narrowed anteriorly, widest near middle, with concave anterior and convex posterior margins, posterolateral corners distinct ( Fig. 15 ). Dorsal and ventral shields present. Dorsal shield large, narrowed anteriorly and bearing setae Oi, Hi, Sci and Li; glandularia Li open on small tubercles. Dorsal furrow complete. Anterolateral corners of coxal plates I and II pointed, extending beyond the anterior idiosoma margin ( Fig. 16 ). Medial margin of coxal plates III twice shorter than medial margin of coxal plates IV, posterior coxal groups separated by a narrow interspace; lateral projection of coxal plate IV not reaching the lateral margin of the idiosoma. Gonopore large (L 145–165), placed slightly posterior to middle of the idiosoma; each genital flap with two patches, connected by a narrow link, genital flap wider than distance between posterior coxal groups; acetabular plates wide with 3 anteromedial and 2 posteromedial thin setae; glandularia Pe located between posteromedial margin of fourth coxae and genital plates; setae and glandularia Se on posterolateral corners. Pedipalps as in male but femur with three dorsodistal, 1 mediodistal and one- two ventrodistal setae or with four dorsodistal and two ventrodistal setae; genu with single mediodistal seta.

Measurements, n=2. L of idiosoma 1088 – 1224, W 1003–1037; L of dorsal shield 755–884, width 646–680; distance between setae Oi–Oi 158–172, distance between setae Hi–Hi 403–442, distance between setae Sci–Sci 370–436, distance between setae Li–Li 270–284; distance between medial margins of coxal plates IV 53 –70; L of genital flaps 145–165, W 73–83; L of genital plates 205–211, W 383–415; L of basal segment of chelicerae 122– 135, L of cheliceral stylet 75–97; L of pedipalpal segments (P-1–5): 38–40, 94–97, 75–78, 110–135, 43–45; L of leg segments: I–Leg- 1–6—90 –92, 148–154, 154–158, 198–205, 178–189, 218–221; II–Leg- 1–6—80 –82, 140– 170, 178–183, 218–220, 210–212, 218–230; III–Leg-1–6—110–120, 152–170, 172–189, 222–224, 210–224, 224– 238; IV–Leg-1–6—151–158, 231–243, 242–244, 277–284, 211–224, 218–220.

Differential diagnosis. The new species is similar to the European species Arrenurus crenatus Koenike, 1896 . The male of A. crenatiformis sp. n. differs from A. crenatus by the following characters (characters states of male A. crenatus are given in parentheses, data taken from Viets 1936; Sokolow 1940): hyaline membrane absent (present), petiole elongate, ratio L/ W 1.63 –1.66 (as long as wide), ligulate process of petiole pointed and located in anterior half of the petiole (large and located in posterior half of the petiole), the bases of setae Pi, Si and Ci located caudally (ventrally), acetabular plates reaching lateral margin of the idiosoma (extending well up the sides of the idiosoma). The genital plates in the female A. crenatus are narrowed laterally ( Koenike 1908); in contrast, the genital plates are not narrowed laterally in the female A. crenatiformis .

Etymology. The species is named crenatiformis as it has many features in common with the European species A. crenatus .

Habitat. Running waters.

Distribution. Asia ( Russia: Far East, Amurskaya Area).

Figures

FIGURES 10 – 11. Arrenurus crenatiformis sp. n., male: 10, idiosoma, dorsal view; 11, idiosoma, ventral view. Scale bar = 100 µm.

FIGURES 12 – 14. Arrenurus crenatiformis sp. n., male: 12, pedipalp; 13, telofemur, genu, tibia and tarsus of leg IV; 14, claw of leg IV. Scale bars = 100 µm for Fig. 13; 50 µm for Figs. 12, 14.

FIGURES 15 – 16. Arrenurus crenatiformis sp. n., female: 15, idiosoma, dorsal view; 16, idiosoma, ventral view. Scale bar = 100 µm.