Atractides (Atractides) ildicus, Tuzovskij, Petr V., 2011

Tuzovskij, Petr V., 2011, Four new water mite species of the genus Atractides Koch (Acari: Hydrachnidia: Hygrobatidae) from Russia, Zootaxa 2738, pp. 41-59 : 50-53

Atractides (Atractides) ildicus , sp. n.

( Figs. 30–39 )

Type series. Holotype: female, slide 8858, Russia, Yaroslavl Province, Nekouz District, Ild stream near village Mar’ino, 9.06. 2003, coll. P.V. Tuzovskij. The river bottom: stones, pebbles and sand, depth 0.3–0.5 m. The holotype is deposited in the collection of Institute for Biology of Inland Waters (Borok, Russia). Paratypes: two females is collected in Ild stream, same locality as holotype, 21.07. 2003 (coll. P.V. Tuzovskij).

Diagnosis. Female: setae Fch heaviest and longer of all dorsal setae; setae Oe, Hi and He shorter and thinner than Fch; other idiosomal setae short hair–like; caudal margin of coxal plates I slightly convex, apodemes of coxal plates II in obtuse angle, pedipalpal femur with ventrodistal protruding; bases of ventral setae divide pedipalpal tibia into three approximately equal sectors (1:1:1); sword seta on P–IV shorter than distance between bases of ventral setae, base of sword seta placed near ventrodistal seta.

Description. Female. Color yellowish–brown. The body flat oval, integument soft with very fine strips. Number and position of idiosomal setae typical for representatives of the genus Atractides . Setae Fch heaviest and longer of all dorsal ones ( Fig. 30 ). Setae Oe, Hi and He shorter and thinner than Fch; other idiosomal setae short hair– like. Setae Fp and Oi without glandularia, other dorsal setae associated with glandularia. First pair of lyriform organs (i1) situated close to posterior eye lenses; i2, in interval between setae Ve and He; i3, behind humeral row of setae (Hi, He); i4, more or less corresponding to lumbar row of setae (Li, Le); i 5 in the posterior part of the dorsum. Coxal plates covering less than half of the ventral surface of body. Posteromedial margin of coxal plates I+II wide slightly convex, with short wide median process and two short apodemes which forming obtuse angle ( Fig. 31 ). First coxal plates fused to each other, but median suture line between them distinct. The seta and glandularium Hv situated in posterolateral part of coxal plate II. Medial margin of coxal plate IV oblique and nearly straight, directed posteromedially; seta Pe situated near middle of anterior margin of coxal plate IV; posterior margin of coxal plate IV slightly convex. Capitulum elongate, rostrum rather long, slightly reaching anterior edge of the capitulum. The setae Ci and Pi separated ( Fig. 32 ). Setae Pi without glandularia, other ventral idiosomal setae associated with glandularia. Excretory pore unsclerotized. Genital plates ( Fig. 33 ) elongate and narrow (ratio length/width 2.7–3.5) with 3 acetabula and 15–19 fine setae each; genital acetabula in arc line, posterior acetabulum larger than anterior and median acetabula. Gonopore longer than genital plates, anterior genital sclerite considerably wider than posterior sclerite. Chelicera with large basal segment and short stylet ( Fig. 34 ). Cheliceral stylet with a few small teeth on dorsal side.

Pedipalp ( Fig. 35 ) slender; trochanter short, with a single short dorsodistal seta; femur with ventrodistal protruding, with 3 short dorsoproximal setae and two long unequal dorsodistal setae. Pedipalpal genu slightly longer than femur with straight ventral margin, with 4 thick unequal dorsal setae and 4–6 thin subequal setae. Pedipalpal tibia very slender, with slightly convex dorsal margin; bases of ventral setae divide tibia into three approximately equal sectors (1:1:1); with a few dorsolateral setae which located mainly in distal half of segment. Ventrolateral sword-like seta moderately in length and shorter than distance between bases of ventral setae, base of sword-like seta placed near ventrodistal seta. Pedipalpal tarsus slightly tapering distally, all spines and thin setae located in distal half of segment.Genu of leg I ( Fig. 36 ) with parallel dorsal and ventral margins, with two short ventroproximal spine near middle of segment, two rather long ventrodistal spines and a few fine setae. Tibia of leg I very slightly thickened distally; bases of setae S1 and S2 separated; S2 shorter and slightly wider than seta S1, both setae more or less pointed. Tarsus I short, ratio length tibia/tarsus = 1.37–1.39; with weakly convex dorsal and concave ventral margins; slightly thickened proximally and distally, with minimum thickness near middle of the segment. Posterior legs, in particular legs IV, very slender; genu and tibia with rather numerous thin and thick setae, tarsus with single ventral spine near middle of segment ( Fig. 37 ). Claws of leg I ( Fig. 38 ) smaller than claws of legs II–IV ( Fig. 39 ). All claws with two pointed denticles, an internal denticle shorter than external denticle, claw lamella with concave ventral margin.

Measurements (n=3). Length of body 785–1090; length of setae Fch 135–150, length of setae Oe, Hi and He 90–105; length of coxae I+II 245–270, width 365–475; length of medial portion of coxae I 100–120; length of coxae III+IV 255–290, width 215–240; lengths of genital plate 100–125, width 36–42; length/width of genital acetabula (ac. 1–3): 36–42/24–30, 36–42/24–30, 38–45/36–42; length of basal segment of chelicera 113–115, length of cheliceral stylet 41–43; lengths of pedipalpal segments (P–1–5): 33–36, 90–96. 102–108, 125–132, 33– 38; length/width of sword seta on P–4: 24–30/6–7; lengths of leg segments: I–Leg. 1–6—65 –72, 100–110, 135– 145, 210–215, 215–220, 155–165; II–Leg. 1–6—65 –70, 85–95, 100–125, 180–195, 190–205, 175–185; III–Leg.

1–6—65 –72, 90–95, 135–140, 210–225, 225–245, 180–210; IV–Leg. 1–6—130–155, 135–150, 215–230, 240– 290, 300–325, 240–260; tibia of leg I: length of seta S1 95 –102, width 8–9; length of seta S2 72 –78, width 10–12, distance between bases of setae S1 and S 2 18 –24.

Differential diagnosis. The new species is closely related to Atractides clavipalpis (Lundblad, 1956) and A. samsonellus Tuzovskij, 2006 . The new species differs from A. clavipes in the following characters (character states of female A. clavipalpis are indicated in parenthesis from Gerecke 2003): the caudal margin of coxal plates I slightly convex (strongly convex), the apodemes of coxal plates II in obtuse angle (in acute angle), the tibia of leg I without distally protruding (with distally protruding near insertion S1); the pedipalp rather long, total length 385– 410 µm (relatively short, total length 364 µm); the sword setae (S1 and S2) on tibia of leg I short, respectively 95– 102 and 72–78 µm (relatively long, respectively 121 and 92 µm), the pedipalpal femur with ventrodistal protruding (without ventrodistal protruding). The gonopore and genital plates in female A. samsonellus subequal in length, the excretory pore plate is surrounded by narrow sclerotized ring, the setae S1 and S2 on tibia of leg I nearly subequal in shape, leg claws with short internal denticle with rounded tip and long pointed external denticle, P-2 with convex ventrodistal protrusion ( Tuzovskij 2006); in contrast, in female A. ildicus the gonopore longer than genital plates, the excretory pore plate unsclerotized, the setae S1 and S2 on tibia of leg I heteromorphic, leg claws with approximately subequal pointed denticles, P-2 with flat ventrodistal protrusion.

Etymology. The species is named after the stream where it was collected (Ild).

Habitat. Running waters.

Distribution. Europe ( Russia, Yaroslavl Province).

Figures

FIGURES 30 – 34. Atractides ildicus sp. n., female: 30, dorsal view; 31, capitulum and coxal plates I – IV; 32, excretory pore, setae Ci and Pi; 33, genital field; 34, chelicera. Scale bars: 30 = 200 µm, 31 – 34 = 100 µm.

FIGURES 35 – 39. Atractides ildicus sp. n., female: 35, pedipalp; 36, genu, tibia and tarsus of leg I; 37, genu, tibia and tarsus of leg I; 38, genu, tibia and tarsus of leg IV; 39, claw of leg I; 40, claw of leg IV. Scale bars: 35 = 50 µm; 36 = 100 µm; 37 = 200 µm; 38 – 39 = 20 µm.