Atractides (Atractides) filimonovae, Tuzovskij, 2022

Tuzovskij, Petr V., 2022, Two new water mite species of the genus Atractides Koch (Acari, Hydrachnidia, Hygrobatidae) from Asia, Zootaxa 5188 (2), pp. 195-200 : 195-198

Atractides (Atractides) filimonovae sp. n.

( Figs 1–7 )

Type material. Holotype: male, slide 9954, Asia, Russia, Western Siberia, Khanty-Mansi Autonomous Okrug, State Nature Reserve “Malaya Sosva”, Emugan stream, 61°47′10.8″N 64°30′32.2″E, 13.07.2019, depth 0.5 m, substrates: stones, sand, leg. M. Filimonova.

Diagnosis. Male. Coxal plates I+II close to coxal plates III+IV but not forming a coxal shield; capitular bay Ushaped. genital plate wider than long, anterior margin slightly convex, with 27–28 setae on each side; P-2 with very large ventrodistal protrusion, P-3 with six thick setae, ventral margin straight; I-Leg-5 S-1 distinctly thinner than S-2, S-1-2 separation 12–13.

Description. Male. Colour in life unknown. The idiosoma oval, integument soft and smooth, muscle insertions unsclerotized. Coxal plates I+II close to coxal plates III+IV at their touching edges, but not forming a coxal shield ( Fig. 1 ). Posteromedial margin of coxal plates I+II rather broad and slightly convex, apodemes of coxal plates II in an acute angle in relation to idiosoma midline. Median suture line between coxal plates I distinct, central sub-dermal projection very small and reaching to posterior margin. Capitular bay U-shaped. The seta and glandularium Hv situated in posterolateral part of coxal plate II. Medial margin of coxal plates III+IV in an obtuse angle, base and glandularium of seta Pe situated near middle of anterior margin of coxal plate IV, posterior margin of coxal plate IV slightly convex. Genital plate ( Fig. 2 ) wider than long (L/W ratio 1.2), anterior margin slightly convex, posterior margin moderately indented, bearing 27– 28 fine setae on each side, acetabula rather large in an obtuse triangle. The setae Pi and Ci separated, excretory pore unsclerotized ( Fig. 3 ).

Pedipalp ( Fig. 4 ) stout: P-1 short, thin with a single short dorsodistal seta; P-2 with very large ventrodistal protrusion, bearing five unequal dorsal setae; P-3 with six thick setae (four dorsal, two ventrodistal) and two to three thin ones, ventral margin straight; P-4 stocky, slightly protruding near proximoventral seta, sword seta short pointed located between ventral setae, bases of ventral setae divide tibia into three unequal sectors (3:3:2), dorsolateral setae numerous located in central and distal parts of segment.

All legs without swimming setae. I-Leg-5 seta S-1 and S-2 distally narrowed ( Fig. 5 ), bluntly pointed, S-1 longish, S- 2 thicker than S-1, proximally enlarged, distance between S-1 and S-2 short; I-L-6 curved, basally thickened, distally with parallel dorsal and ventral margins, much shorter than I-Leg-5 (I-Leg-5/6 ratio 1.32). Posterior pairs of legs, in particular IV legs, very slender, with a few setae on each segment ( Fig. 6 ). Leg claws with two pointed denticles, internal denticle a little shorter than external one; lamella of with slightly concave ventral margin ( Fig. 7 ).

Measurements (n=1). Idiosoma L 600; coxal plates I+II L 265, W 300, mL 125; coxal plates III+IV L 205, W 180; genital plate L 120, W 145; genital acetabula (ac. 1–3) L/W 54/36, 48/30, 48/36; glandularia D: 18–20; pedipalp total L 294, L/H, L/H ratio: P-1, 36/30, 1.2; P-2, 72/63, 1.14; P-3, 78/54, 1.44; P-4, 84/54, 1.55; P-5, 24/12, 2.0; leg segments, L, L/H ratio: I–Leg-1, 54/48, 1.12; I–Leg-2, 60/48, 1.25; I–Leg-3, 90/42, 2.14; I–Leg-4, 140/48, 2.87; I–Leg-5, 175/55, 3.05; I–Leg-6, 115/30, 3.8; II–Leg-1–6, L: 54, 65, 80, 115, 120, 115; III–Leg–1–6, L: 60, 60, 85, 125, 140, 120; IV–Leg–1–6, L: 120, 110, 145, 180, 200, 150; I-Leg-5/6 ratio 1.33; I-Leg-6: HA 32, HB 19, HC 21; I-Leg-6, distance between S-1 and S-2 12 –13, S-1 L/W, L/W ratio 90–10, 9.0, S-2 L/W, L/W 66/12, 5.5, L ratio S-1/ S-2 1.36.

Female. Unknown.

Remarks. The present species is similar to Atractides (Atractides) alaarchaensis Pešić & Smit, 2018 and A. (Atractides) sonkulensis Pešić & Smit, 2018 in the structure of pedipalp. The new species differs from A. alaarchaensis in the following characters (character states of male A. alaarchaensis are indicated in parenthesis, data from Pešić & Smit 2018): Integument smooth (striated); genital plate wider than long, L/W 120/145 (almost as long as wide, 117– 128/123–134; genital plate with 27–28 setae on each side, Fig. 2 (with 13–14 setae on each side, Fig. 8 ), pedipalp short, total L 294 (relatively long, total L 304–317), P-2 with very large ventrodistal protrusion, Fig. 4 (ventrodistal protrusion comparatively slightly developed, Figs 9-10 ), I-Leg-5/6 L ratio 1.33 (1.43). The male A. sonkulensis differs from A. filimonovae sp. n. in coxal field merged to an unique plate, including Vgl-3 (= Pe), P-2 and P-3 with straight ventral margin, genital plate with 14-16 setae on each side ( Pešić & Smit 2018).

Etymology. The species is named after the collector, Maria Filimonova.

Habitat. Running waters.

Distribution. Asia: Russia, Western Siberia: Khanty-Mansi Autonomous Okrug.

Figures

FIGURES 1–4. Atractides filimonovae sp. n., male: 1, coxal plates; 2, genital plate; 3, excretory pore, seta Pi and Ci; 4, pedipalp, lateral view. Scale bars: 1= 100 µm, 2, 3, 4 = 50 µm.

FIGURES 5–7. Atractides filimonovae sp. n., male: 5, tibia and tarsus of leg I; 6, IV-Leg-4-6; 7, leg claw. Scale bars: 5, 7 = 50 µm, 6 = 100 µm.

FIGURES 8–10. Atractides alaarchaensis, male: 8, genital plate; 9-10, pedipalp (from Pešić & Smit 2018). Scale bar: 8-10 = 100 µm.