Hygrobates (Hygrobates) gusakovi, Tuzovskij, Petr V., 2013

Tuzovskij, Petr V., 2013, New water mite species (Acari, Hydrachnidia) from Vietnam, Zootaxa 3700 (4), pp. 547-560 : 554-556

Genus Hygrobates Koch, 1837

Hygrobates (Hygrobates) gusakovi sp. n. ( Figs 18–22 )

Holotype: female, slide 9697, Vietnam, Dong Nai (Đồng Nai) Province, Cat Tien (Cát Tiển) National Park, forest stream Dak Lua (Đák Lua) (N 11°29.844, E 107°22.847), altitude 136 m, water depth 0.3 m, collecting substrate: coarse plant residues, water temperature 26.2°С, dissolved oxygen 3.2 mg/l, рН 6.2, conductivity 304 ΜS/cm, 13 May 2012 (leg. V.A. Gusakov).

Diagnosis. Male: medial margin of coxal plates III+IV concave, genital field with three acetabula and eight small thin setae on each side, acetabula obtuse triangular-shaped, genital field fused anteriorly with two relatively large anterior glandularia.

Description. Male. Idiosoma oval, integument soft and smooth. The number and position of idiosomal setae typical for the genus Hygrobates . Coxal plates covering less than half of the ventral surface of idiosoma ( Fig. 18 ). Posteromedial margin of coxal plates I+II rounded, with two moderately large apodemes. Suture line between coxal plates I well developed. Medial margin of coxal plates III+IV concave, setae Pe situated near middle of anterior margin of coxal plates IV, posteromedial corner of coxal plate IV acute. Posterior edge of coxal plate IV directed obliquely–posteromedially. Excretory pore unsclerotized, placed between setae Ci. Genital field ( Fig. 19 ) with three acetabula and eight small thin setae on each side, acetabula obtuse triangular-shaped. Genital field fused anteriorly with two relatively large anterior glandularia (gg in Fig. 19 ).

Chelicera ( Fig. 20 ) with large basal segment and short crescent claw. Pedipalp ( Fig. 21 ) robust: P-1 short with single dorsal seta; P-2 large with five dorsal setae, ventral margin slightly convex, with several ventrodistal teeth (distinctly visible only 4–5 relatively large distal teeth); P-3 with to two short proximal setae and two unequal dorsodistal setae, with a few teeth in the distal half of the segment; P-4 slender, ventral setae relatively thick and located near the distal end of segment.

Legs without swimming setae. I—Leg-5 with two subequal pointed spine-like setae ( Fig. 22 ). All leg claws with two denticles, internal denticle shorter than external denticle; claw blade slightly developed with slightly convex ventral margin ( Fig. 23 ).

Measurements (n=1). Idiosoma L 590, W 470; coxal plates I–IV L 275, W 350; L of median portion of coxae I 110; genital field L 90, W 115; basal segment of chelicera L 155, cheliceral claw L 48; pedipalpal segments (P-1– 5) L: 21, 72, 66, 95, 21; L of leg segments: I—Leg-1–6: 42, 65, 87, 105, 110, 108; II—Leg-1–6: 42, 72, 85, 108, 115, 115; III—Leg-1–6: 48, 72, 90, 120, 130, 125; IV—Leg-1–6: 115, 95, 130, 170, 190, 175.

Remarks. The new species is similar to Hygrobates hamatus bharatensis Cook, 1967 . The genital field in male of Hygrobates gusevi sp. n. bears two large glandularia and the medial margin of coxal plates III+IV is concave, while in the male of H. hamatus bharatensis the genital field is without glandularia and the medial margin of coxal plates III+IV is straight or slightly convex (Cook 1967).

Etymology. The species is named after Dr. Vladimir Gusakov.

Habitat. Running waters.

Distribution. Asia ( Vietnam: Dong Nai Province)

Figures

FIGURES 18 – 20. Hygrobates gusakovi, sp. n. male: 18, idiosoma, ventral view; 19, genital field; 20, chelicera. Scale bars: 18 = 100 Μm; 19, 20 = 50 Μm.

FIGURES 21 – 23. Hygrobates gusakovi, sp. n. male: 21, pedipalp, lateral view; 22, genu, tibia and tarsus of leg I; 23, claw of leg IV. Scale bar: 50 Μm.