Atractides (Atractides) yaroslavlensis, 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 : 42-50

Atractides (Atractides) yaroslavlensis , sp. n.

( Figs 1–29 )

Type series. Holotype: female, slide 9029, Russia, Yaroslavl Province, Breitovo District, the Kamenka stream near the village of Sit’–Pokrovskoe, depth 0.3–0.5 m; substrates: stones, sand and mosses, 8. 08. 2004, coll. P.V. Tuzovskij. The holotype is deposited in the collection of Institute for Biology of Inland Waters (Borok, Russia). Paratypes: one female, one male and six larvae from the same locality and collection date as holotype. Larvae reared from one female (holotype) in laboratory. The duration of the embryonic period at room temperature was 12 days.

Additional material. 17 females and 12 males, Russia, Yaroslavl Province, Nekouz District, the Ild river near the village of Mar’ino, June–August 2004–2005, coll. P.V. Tuzovskij.

Diagnosis. Adults: posterior edge of coxal plate IV obliquely–posteromediallydirected, tarsus of female leg I long and slender (ratio L tibia/tarsus 1.25–1.32), pedipalpal femur of male with large ventrodistal projection; larva: dorsal shield elongate (ratio length/width 1.64–1.70) with parallel lateral edges, posterior margin of basal segments of chelicera convex with small median incision, seta C3 considerably shorter than C4.

Description. Female. Color yellowish–brown, mature specimens nearly black. The body flat, oval, integument soft with very fine strips. Setae Fch longest and heaviest of all dorsal setae ( Fig. 1 ). Setae Oe, Hi and He shorter than Fch but considerably longer and thicker than other idiosomal setae. Setae Fp and Oi without glandularia, other dorsal setae associated with glandularia. First pair of lyriform organs (i1) situated behind 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 or ventrum. In mature specimens coxal plates covering less than half of the ventral surface of body ( Fig. 2 ). Posteromedial margin of coxal plates I+II usually rounded, but sometimes straight, with short median process and two moderately large apodemes; median suture line between coxal plates I distinct. The seta and glandularium Hv situated in posterolateral part of coxal plate II. Medial margin of coxal plates III+IV rounded, setae Pe situated near middle of anterior margin of coxal plate IV. Posterior edge of coxal plate IV obliquely-posteromedially directed. The setae Pi without glandularia and usually separated from setae Ci, but sometimes both setae located on a common sclerite. Other ventral idiosomal setae associated with glandularia. Excretory pore unsclerotized, placed between or slightly behind setae Ci. Gonopore and genital plates subequal in length, or gonopore slightly longer than plates. Each genital plate with 3 acetabula and 16–22 fine setae.

Genital plates narrow elongate, ratio length/width 3.1–3.4; genital acetabula in arc line, posterior acetabulum larger than anterior and median acetabula ( Figs 3–4 ), but occasionally genital plate with two acetabula ( Fig. 5 ). Anterior genital sclerite considerably wider than posterior sclerite.

Chelicera ( Fig. 6 ) with large basal segment and short crescent-shaped stylet. Cheliceral stylet with small teeth on concave side. Pedipalp ( Fig. 7 ) slender; trochanter short, with a single dorsodistal seta; femur with straight ventral margin with 5 unequal dorsal setae. Pedipalpal genu with straight ventral margin, with 4 thick and 4–6 thin setae. Bases of ventral setae divide tibia into three approximately equal sectors (1:1:1), ventrolateral sword-like seta rather large and placed near middle of segment in space between ventral setae; dorsolateral setae relatively not numerous and located mainly in distal half of segment. Pedipalpal tarsus slightly tapering distally, with one solenidion, 4 thick spines and 5 fine setae; all setae located in distal half of segment.

Capitulum ( Fig. 9 ) elongate, rostrum short, not reaching anterior edge of capitulum; dorsal hypostomal setae longer than ventral setae.

All legs without swimming setae. Tibia of leg I ( Fig. 8 ) slightly thickened distally; bases of setae S1 and S2 separated, narrowed proximally; seta S2 shorter and wider than S1, both setae more or less pointed. Tarsus I long and slender, ratio length tibia/tarsus 1.25–1.32; with convex dorsal and concave ventral margins; slightly thickened proximally. Posterior legs, in particular legs IV, very slender; distal ends of genu and tibia with rather long thick unequal setae ( Fig. 10 ). Claws of leg I ( Fig. 11 ) smaller than claws of legs II–IV ( Fig. 12 ). All leg claws with two denticles, internal denticle slightly longer than external denticle; lamella with slightly concave ventral margin.

Measurements (n=10). Length of body 750–1250; length of setae Fch 140–160, length of setae Oe Hi and He 80–110, length of coxae I+II 250–300, width 340–365; length of medial portion of coxae I 115–125; length of coxae III+IV 245–270, width 220–245; lengths of genital plate 142–150, width 42–48; length/width of genital acetabula (ac. 1–3): 42–45/24–27, 40–42/30–36, 48–55/ 40–48; length of basal segment of chelicera 210–215, length of cheliceral stylet 78–85; length of pedipalpal segments (P1–5): 35–42, 78–90, 108–125, 115–140, 30–36; length/width of sword seta on P4 33–39/6–7; lengths of leg segments I–Leg.1–6: 65–78, 105–138, 150–180, 225– 265, 225–270, 180–205; II–Leg. 1–6: 60–72, 90–105, 125–150, 185–205, 190–205, 185–195; III –Leg. 1–6: 65– 85, 95–110, 125–155, 195–235, 205–240, 190–220; IV–Leg. 1–6: 125–150, 125–155, 195–235, 270–315, 275– 335, 230–275; tibia of leg I: length of seta S1 130–140, width 12–13; length of seta S2 102–115, width 17–19; distance between bases of setae S1– S 2 24 –30.

Male. Dorsal surface, coxae of legs similar to female, from which it differs in smaller size, as well as shape of genital field, pedipalp and terminal segments of leg I. Coxae of legs covering larger than one half of ventral surface. Suture line between coxae I clearly developed, central sub–dermal projection short; apodeme of coxal plates II rather long, reaching anteromedial margin of coxal plates III ( Fig. 15 ). Posteromedial margin of coxae I convex. Setae Hv located in lateral portion of coxae II. Coxae IV trapezoidal, their medial margins rather wide and rounded; glandularia Pe situated near anterior margins of coxae IV. Posterior edge of coxal plate IV obliquely –posteromedially directed. Setae Pi without glandularia and usually separated from setae Ci, but sometimes both setae located on a common sclerite, excretory pore unsclerotized.

Genital plates fused to each other by anterior and posterior ends and forming small anterior and rather deep posterior median incisions ( Fig. 13–14 ). Posterior pair of genital acetabula large, oval or triangular and considerably larger than two anterior pairs of acetabula. Genital plate with 23–32 fine setae on each side, three of them longer than others; genital opening narrow. Genital plate usually wider than long ( Fig. 13 ), but occasionally length and width nearly subequal ( Fig. 14 ).

Pedipalp ( Fig. 16 ) stout; trochanter short, with a single short dorsodistal seta; femur with widely rounded ventrodistal protrusion (hump) and relatively large angular projection (protuberance) which reaches well beyond the protrusion, with five dorsal (two proximal and three distal) unequal setae. Pedipalpal genu with slightly concave ventral margin and convex dorsal margin, two proximal and two distal thick unequal setae and 4–5 fine setae. Pedipalpal tibia narrowed proximally with convex dorsal edge and very numerous dorsolateral setae, bases of two ventral setae divide tibia into three unequal sectors (1–1–2); sword–like seta rather large, considerably longer than distance between ventral setae.

Genu of leg I ( Fig. 17 ) thickened distally; tibia with nearly parallel ventral and dorsal margins; seta S1 longer and thinner than S2, both these setae more or less pointed, narrowed proximally; tarsus relatively short, slightly thickened proximally, with slightly convex dorsal margin and concave ventral one.

Measurements (n=10). Length of body 630–750; length of setae Fch 150–190, length of setae Oe Hi and He 95–130; length of coxae I+II 250–275, width 285–385; length of medial portion of coxae I 115–135; length of coxae III+IV 190–230, width 145–230; lengths of genital plate 100–125, width 125–140; length/width of genital acetabula (ac. 1–3): 36–42/28–30, 36–42/24–30, 48–65/35–42; length of basal segment of chelicera 150–160, length of cheliceral stylet 65–70; lengths of pedipalpal segments (P–1–5): 30–36, 65–80, 70–85, 90–105, 29–31; length/width of sword seta on P4 36–42/6–7; lengths of leg segments: I–Leg. 1–6: 60–66, 90–105, 120–140, 180– 210, 185–215,135–155; II–Leg. 1–6: 55–72, 70–85, 100–120, 130–155, 140–160, 135–155; III–Leg. 1–6: 55–75, 75–90, 105–130, 160–185, 180–200, 150–170; IV–Leg. 1–6: 115–140, 105–125, 165–190, 160–250, 225–260, 190–205; tibia of leg I: length of seta S1 100–120, width 9–11; length of seta S2 90 –96, width 12–14, distance between setae S1 and S 2 18 –30.

Larva. Idiosoma flat and oval in shape, dorsal shield in unengorged larva covers nearly all dorsum ( Fig. 18 ). Dorsal shield elongate, ratio length/width 1.64–1.70, with straight or slightly convex anterior margin, indented anterolaterally, with parallel lateral edges, and bears four pairs of setae in anterior portion: two pairs of simple setae (Fch, Vi) and two pairs of trichobothria (Fp, Oi). Simple setae thick and long, anterior setae (Fch) considerably shorter than posterior setae (Vi). Both pairs of trichobothria short, thin and subequal in length. Seven pairs of setae (Oe, Hi, He, Sci, Sce, Li, Si) are situated on soft wrinkled membrane. Setae Hi and Sci longest and heaviest of all dorsal setae situated on soft membrane. Setae Oe slightly shorter than setae Hi and Sci but longer than other dorsal setae situated on soft membrane. Setae Hi and He located close to each other, setae Sci and Sce divided by wide interspace. Dorsal shield with reticulated pattern consisting of elongated cells.

Coxae I–III fused to each other on each side, suture line between them developed only in their lateral parts ( Fig. 19 ). Coxal plates I–III straight posteromedially and fitting closely with anterior margin of excretory pore plate. Both setae (C1, C2) on coxae I short and approximately subequal in length. Lateral seta (C3) considerably shorter than medial seta on coxae IV (C4). Setae C4 not extending to posterior margin of coxal plates I–III. All coxal plates with reticulated pattern consisting of elongated cells. Transverse muscle attachment scar on coxae III not developed. Urstigma with cap, very small, occupies lateral position on border between coxae I and II. Setae Ci very long, whip-like, well thickened and borne on rather large projections. Setae Le and Se fine and short.

Excretory pore plate ( Fig. 20 ) large, nearly twice as wide as long and bearing four pairs of setae (Ai, Ae, Pi, Pe). Both pairs of anal setae (Ai, Ae) reduced and represented by alveoli. Distance between setae Ae–Ae slightly longer than distance between setae Ai–Ai. Setae Pi slightly shorter than setae Pe, bases of both pairs of these setae placed on anterior margin of excretory pore plate. Excretory pore situated proximally to middle of excretory pore plate near setae Ae.

Capitulum ( Fig. 21 ) elongate with rather wide base and narrow rostrum, anterior and posterior pairs of setae approximately subequal. Basal part of capitulum twice as long as rostrum.

Basal segments of chelicerae fused to each other medially, their posterior edges convex with small median incision ( Fig. 22 ). Cheliceral stylet small, crescent–shaped with one subapical tooth ( Fig. 23 ).

Pedipalps relatively short ( Fig. 24 ). Trochanter very short, fused with femur but suture line between these segments present. Pedipalpal femur with one short, thin dorsodistal seta; genu with very long, thick proximal seta and short, fine dorsodistal one; tibia with two long unequal setae and massive dorsodistal claw; tarsus small, with one rather long solenidion and short, thin simple unequal setae.

Legs 5–segmented and without swimming setae. Shape and arrangement of setae on legs segments as shown in Figs 25–27 . Total number of leg setae, excluding eupathidia, as follows (specialized setae indicated in parenthesis): I– Leg. 1–5: 1, 7, 5 (s), 11 (2s), 14 (s, ac); II–Leg. 1–5: 1, 7, 5 (s), 11 (2s), 14 (s, ac); III–Leg. 1–5: 1, 6, 5 (s), 10 (s), 11 (ac). Trochanter of legs I with thick and relatively short seta, trochanter of legs II and III each with rather long thin seta. Solenidion on genu leg I and leg II considerably longer than solenidion on genu III. Solenidia on tibia of leg I and II located at distal end of segment. Proximal solenidion on tibia of leg I and II longer than distal solenidion. Solenidion on tarsus of leg I occupying dorsodistal position, solenidion on tarsus II situated proximally. Genu of leg III with short solenidion and tibia III with long solenidion. Acanthoid seta located distally on tarsus of all legs. Claws of legs III ( Fig. 28 ) larger than claws of legs I and II ( Fig. 29 ). Central claw and lateral claws each pair of legs nearly subequal in size. All claws with a few fine lateral teeth.

Measurements (n=6). Length of dorsal plate 230–245, width 145–150; length of setae Fch 29–38, length of setae Fp and Oi 9–13, length of setae Vi 60 –70, length of setae Oe 50–60, length of setae Hi 64–70, length of setae He 25–32, length of setae Sci 65–74, length of setae Sce 22–29, length of setae Li 22–26, length of setae Si 22–29, length of setae Ci 145–157, length of setae Se 25–29, length of setae Le 22–26, length of setae Pi 15–19, length of setae Pe 16–23, length of setae C 1 16–23, length of setae C 2 16–21, length of setae C3 38–48, length of setae C4 64–75; length of medial edges of coxae I–III 155–170; length of capitular bay 41–45; diameter of urstigma 11–13; length of excretory pore plate 40–45, width 75–80; length of capitulum 70–76; length of basal segment of chelicera 64–75, length of cheliceral stylet 18–23; length of pedipalpal segments (P–1–5): 4–5, 32–35, 16–19, 8–10, 4–5; length of basal projection for insertion Ci 12–16, diameter of basal projection for insertion Ci 9–11; distance between setae Ai–Ai 14–17, distance between setae Ae–Ae 19–23; length of legs segments: I–Leg. 1–5: 25–32, 32– 35, 29–35, 38–42, 44–50; II–Leg. 1–5: 28–32, 32–35, 32–35, 41–45, 50–55; III–Leg. 1–5: 35–38, 41–45, 41–45, 54–58, 55–60.

Differential diagnosis. The present species is closely related to Atractides nodipalpis Thor, 1899 and A. magadanensis Tuzovskij, 2010 . The new species differs from A. nodipalpis in the following characters (character states of adults and larva A. nodipalpis are indicated in parenthesis from Gerecke 2003 and Wainstein 1980 respectively): both sexes—posterior edge of coxal plate IV obliquely posteromedially directed (transverse); male—pedipalpal femur with the ventrodistal protrusion consisting of a widely rounded medial hump and relatively large angular protuberance (blindly pointed medial hump and an equally convex short lateral protuberance), P-2 ventral margin 1: 1: 2 (2: 1: 2), sword seta placed near proximodistal seta (near proximoventral seta); female—genital acetabula in arc line (in an obtuse angle); larva—dorsal shield relatively narrow with parallel lateral margins, ratio length/width 1.64–1.70 (rather wide with convex lateral margins, ratio length/width 1.38), posterior margin of basal segments of chelicera convex with small median incision (straight, without median incision), seta C3 considerably shorter than C4 (setae C3 and C4 equal in length).

The new species differs from A. magadanesnsis by the male with posterior pair of the genital acetabula rectangular, P-2 of female with convex ventral margin, leg claws with short blade, both claw denticles approximately subequal in length; larva - the capitular base nearly as long as wide, the excretory pore located in the centre of the excretory pore plate ( Tuzovskij 2010a). In contrast, the male of A. yaroslavlensis has the posterior pair of genital acetabulum oval or triangular, P-2 of female with straight or slightly concave ventral margin, leg claws with relatively long blade, an internal denticle longer than external denticle; larva - the capitular base longer than wide, the excretory pore located in anterior half of the excretory pore plate.

Etymology. The species epithet yaroslavlensis is derived from the name of the Province where it was collected (Yaroslavl).

Habitat. Running waters.

Distribution. Europe ( Russia, Yaroslavl Province).

Figures

FIGURES 1 – 2. Atractides yaroslavlensis sp. n., female: 1, dorsal view; 2, ventral view. Scale bar, 1 – 2 = 100 µm.

FIGURES 3 – 8. Atractides yaroslavlensis sp. n., female: 3 – 5, genital plate; 6, chelicera; 7, pedipalp; 8, genu, tibia and tarsus of leg I. Scale bars: 3 – 5, 8 = 100 µm; 6 – 7 = 50 µm.

FIGURES 9 – 14. Atractides yaroslavlensis sp. n.: 9, capitulum, ventral view; 10, genu, tibia and tarsus of leg IV; 11, claw of leg I; 12, claw of leg IV; 13 – 14, genital plate; 9 – 12 — female, 13 – 14 male. Scale bars: 9 = 50 µm; 10, 13 – 14 = 100 µm; 11 – 12 = 20 µm.

FIGURES 15 – 17. Atractides yaroslavlensis sp. n., male: 15, coxal field; 16, pedipalp; 17, genu, tibia and tarsus of leg I. Scale bars: 15, 17 = 100 µm; 16 = 50 µm.

FIGURES 18 – 19. Atractides yaroslavlensis sp. n., larva: 18, dorsal view; 19, ventral view. Scale bar: 18 – 19 = 50 µm.

FIGURES 20 – 24. Atractides yaroslavlensis sp. n., larva: 20, anal plate; 21, capitulum, ventral view; 22, chelicerae, dorsal view; 23, cheliceral stylet, lateral view; 24, pedipalp, lateral view. Scale bar: 20 – 24 = 20 µm.

FIGURES 25 – 29. Atractides yaroslavlensis sp. n., larva: 25, leg I; 26, leg II; 27, leg III; 28, claws of leg I; 29, claws of leg III. Scale bars: 25 – 27 = 50 µm; 28 – 29 = 20 µm.