Aturus polysetus Semenchenko & Tuzovskij, 2011, sp. n.

Aturus polysetus sp. n.

(Figs. 27–35)

Type series. Holotype: male (385-kas– IBSS), Russia, Sakhalin Area, Dolinsky District, Sea of Okhotsk basin, unnamed spring, N 47°11.415’; E 143°01.239’; depth 30 cm; substrate: cobbles, pebbles, medium-grained sand. 27.09.2009, leg. K.A. Semenchenko. Paratypes: 1 female (386-kas– IBSS), same data as holotype; 1 male (337- kas– IBSS), 1 female (338-kas– IBSS), Russia, Primory Territory, Anuchinsky District, Arsenyevka River basin, spring Pyany near Novogordeevka, N 44°01.032’; E 133°11.174’; depth 10–20 cm; substrate: cobbles, coarsegrained sand. 8.07.2007, leg. K.A. Semenchenko, D.A. Sidorov; 2 males (196-197-kas– IBSS), Russia, Primory Territory, Terneysky District, “Sikhote-Alin State Nature Biosphere Reserve”, Sea of Japan basin, spring Zolotoy; depth 17 cm; substrate: boulders, cobbles, pebbles. 27.05.1999, leg. E.V. Potikha; 1 male (71-kas– IBSS), 1 female (72-kas– IBSS), Russia, Khabarovsk Territory, Ulchsky District, Amur River basin, Sushchevsky Kluch River, 12.10.2006, leg. N.M. Yavorskaya.

Description. Male. Idiosoma almost rounded. Frontal margin convex, with small median incision (Fig. 27). Setae Fp, Oi and Pi without glandularia, other idiosomal setae associated with glandularia. Setae Fch and Oe longer and thicker than proterosomal setae Fp, Vi, Ve and Oi. Setae Vi and first pair of lyriform organs (i1) situated on small platelets. Dorsal surface with porous structure. Dorsal shield separated from ventral shield, transverse ridge situated between setae Hi and Si; 1 piece of muscle attachment scar posterior to eyes on each side of idiosoma, with 6 pairs of setae: Oi, Hi, Si, Se, Ci and Pi; setae Hi long, thick and bifurcated other setae short, thin and simple. Setae Oe, He, Sci and Li situated on soft interscutal membrane. Setae Oe and He bifurcated, Oe twice longer than He. Second pair of lyriform organs (i2) situated posterior to sclerites bearing setae Oe, i3 on sclerites bearing setae Sci, i4 posterior to Sce, i5 on dorsal shield posterior to setae Pi. Excretory pore opens caudally on dorsal shield. Posterolateral surface of dorsum with numerous short, thin, feathered setae, forming 2 transverse rows and numerous long thick and thin setae located distally to distinct rows of setae, 4–7 pairs of spatulate modified setae caudally.

Ventral shield (Fig. 28) with deep median cleft and 9–11 genital acetabula on each side. Setae Pe and Le situated near posterolateral margins of venter. Median cleft with 3–4 thin setae on each side.

Capitulum slightly elongated with short anchoral process. Trochanter of pedipalp (Fig. 29) short, thin with 1 dorsodistal seta. Ventral margin of femur slightly convex, with developed ventrodistal projection. Femur with 3 dorsoproximal setae and 2 dorsodistal ones. Genu with 2 dorsodistal setae, its ventral margin slightly concave. Tibia expanded distally with 2 ventrodistal setae (one thick and one thin), few thin dorsodistal ones and short distolateral spine.

Tibia of leg III (Fig. 30) with 23–29 ventral feathered, 5 dorsal smooth setae and 2 thick curved setae, more proximal of which bearing 3–5, distal 1–3 small tubers. Trochanter of leg IV (Fig. 31) with 2 dorsodistal setae; basifemur IV curved; genu IV expanded distally, with 3 ventrodistal long setae (thin curved seta, thick rounded on tip blade-like and thinner pointed sword-like), with 1 thick short medial and 4 dorsal short setae, 4 distal long setae, 3 of which serrated distally; tibia IV (Fig. 32) with 7 serrated (2 long and 5 shorter), 4 mediodistal ventral smooth and some distal setae of different length; tarsus and tibia approximately subequal, tarsus expanded distally with slightly convex dorsal margin. Claws (Fig. 33) asymmetrical: one claw with very long central denticle and short external and internal denticles (all three denticles with acute tips), other claw with short acute external, longer wide rounded central and longest acute internal denticles.

Measurements (n=3). Length of idiosoma 444–455, width 376–383; length of dorsal shield 373–389, width 284–336; length of capitulum 108–110, width 72–74; length of basal segment of chelicera 94–102, length of cheliceral stylet 32–35; length of capitular bay 102–108; length of pedipalpal segments (P-1–5): 27–32, 62–65, 50–54, 92–100, 32–33; length of leg segments: I-L- 1–6—51 –57, 73–76, 65–67, 92–95, 108–113, 113–116; II-L- 1–6—51 – 62, 72–84, 78–81, 113–116, 122–124, 126–127; III-L- 1–6—54 –75, 97–103, 110–113, 145–146, 178–189, 183– 186; IV-L- 1–6—81 –92, 158–170, 127–137, 162–170, 159–163, 154–159.

Female. Idiosoma flat. Dorsal shield covering nearly all dorsal surface. Frontal margin convex, with small median incision (Fig. 34). Setae Fp, Oi and Pi without glandularia; other idiosomal setae associated with glandularia. Setae Fch and Oe longer and thicker than proterosomal setae Fp, Vi, Ve and Oi. Setae Vi and first pair of lyriform organs (i1) situated on small platelets. Dorsal shield porous, bearing 4 pairs of setae: Oi, Hi, Si, Se, with small indentation in caudal part. Setae Oe, He, Sci, Le, Li and Ci situated on smooth interscutal membrane. Second pair of lyriform organs (i2) situated posterior to sclerites bearing setae Oe, i3 posterior to sclerites bearing setae Sci, i4 posterior to Li, i5 on ventral surface laterally to setae Pi.

Excretory pore opens posterior to dorsal shield on sclerite between setae Ci. Coxal shield (Fig. 35) occupying about 4/5 of ventral surface. Setae Sce and Pe situated between posterior margin of coxal shield and genital plates. Anterior genital sclerite developed. Genital field with 7–9 pairs of acetabula, forming 1 row on plates along posterior margin of each side, each genital plate bearing 2 median thin setae. Pedipalps similar to those of male.

Measurements (n=2). Length of idiosoma 449–508, width 383–422; length of dorsal shield 393–435, width 342–343; length of capitulum 108–120, width 79–81; length of basal segment of chelicera 102–129, length of cheliceral stylet 30–34; length of capitular bay 98–100; length of pedipalpal segments (P-1–5): 26–27, 65–66, 43–48, 89–97, 32–35; length of leg segments: I-L- 1–6—43 –46, 62–67, 51–54, 73–75, 89–92, 94–95; II-L- 1–6—54 –59, 59–70, 57–60, 81–84, 92–102, 97–102; III-L- 1–6—57 –59, 67–76, 67–70, 94–100, 119–124, 118–127; IV-L- 1–6— 78 –86, 102–108, 89–94, 118–124, 132–140, 129–135.

Differential diagnosis. The present species is similar to Aturus mirabilis Piersig, 1896 due to the resembling shape of dorsal shield and the position of the dorsal setae; setae Oe, He and Hi bifurcated, large number (4–7 pairs) of spatulate modified setae caudally, prominent region around the genital cleft, serrated setae on tibia of leg IV. A. polysetus sp. n. differs from A. mirabilis in the following characters (character states of A. mirabilis are given in parentheses, data taken from Mitchell 1956): dorsal shield with transverse ridge situated between setae Hi and Si, posterior margin of dorsum with numerous short and long setae (dorsum without any ridges or setae on posterior margin), genu of leg IV with 3 ventrodistal long setae—thin curved seta, thick rounded on tip blade-like and thinner pointed sword-like (with 2 ventrodistal pointed long setae), genu of leg IV with 2 ventrodistal long setaerounded on tip blade-like and pointed sword-like (the same setae both pointed), tibia of leg IV with 7 serrated setae—2 long and 5 shorter (with 5 serrated setae approximately subequal in length). A. polysetus sp. n. is also closely related to A. pulcher sp. n. (see below) and differs in the following characters (character states of A. pulcher sp. n. are given in parentheses): dorsal shield in males with transverse ridge situated between setae Hi and Si (without transverse ridge, only with depressions in frontal part, posterior to setae Si and Se, and along excretory pore); setae Si and Se subequal in length (setae Se twice longer than Si); no setae located posterolaterally on ventral side (some long setae located posterolaterally on ventral side); ventrodistal projection on ventral margin of pedipalpal femur twice shorter in A. polysetus sp. n. than in A. pulcher sp. n.; tibia of leg III with 23–29 ventral feathered, 5 dorsal smooth setae and 2 thick curved setae, more proximal of which bearing 3–5, distal 1–3 small tubers (with 45–53 smooth setae, 4 ventral of which with 2–5 branches); genu of leg IV with 2 ventrodistal long setae—rounded on tip blade-like and pointed sword-like (the same setae both pointed).

Etymology. The species epithet polysetus is derived from the presence of numerous setae on the dorsum and posterior pairs of legs.

Habitat. Running waters.

Distribution. Russia: Far East, Primory and Khabarovsk Territories, Sakhalin Area.