Sperchon (Hispidosperchon) nevelskoii, Tuzovskij, Petr V. & Semenchenko, Ksenia A., 2009

Tuzovskij, Petr V. & Semenchenko, Ksenia A., 2009, New water mites species (Acariformes: Hydrachnidia) from the Far East of Russia, Zootaxa 2241, pp. 1-21 : 2-3

Sperchon (Hispidosperchon) nevelskoii sp. n.

( Figs. 1–8 )

Type series. Holotype: male (244-kas– IBSS), Russia, Khabarovsk Territory, Ul’chsky District, the Amur River basin, the Pey Khoy River, 30.09.2006, leg. N.M. Yavorskaya.

Description. Male. Body flat and oval. Dorsum with two plates, covering less half of ventral surface ( Fig.1 ). Anterior plate with relatively shallow concave anterior margin, convex lateral margins and wide straight posterior one, bearing setae Oi in posterior half of plate. Posterior plate with wide straight anterior margin, convex lateral ones and rounded posterior end, bearing setae Sci near lateral margin of the plate. Anterior and posterior plates divided by rather large interspace. Setae Fp and Oi without glandularia, other dorsal setae associated with glandularia. Setae Fch, Fp, Vi, eye capsules and first pair of lyriform organs (i1) situated closely together at anterior end of idiosoma. Setae Hi located between anterior and posterior plates; setae Ve, He, Le, Li, Si and four pairs of lyriform organs (i2–i4) situated along lateral edges of idiosoma. Eye capsules relatively large, eye lenses small separated and approximately subequal in size. Frontal organ absent. Dorsal plates with porous surface, soft integument with numerous short teeth, forming net structure ( Fig. 2 ).

Coxae of legs incorporated into four groups and occupy about half of ventral surface of idiosoma ( Fig. 3 ). Posteromedial portions of coxae of legs I–II closely together, but not fused to each other, with slightly developed posteromedial apodemes. Posterior coxal groups widely separated, their combined length greater than width on each side. Setae Pe located in medial portion of coxae III; setae Hv in lateral position between coxae II and III; setae Sce situated behind posterior margin of coxae IV; setae Oe and Se located along lateral edges of idiosoma. Posteromedial setae (Pi and Ci) arranged in longitudinal row. Setae Pi without accompanying glandularia. Excretory pore small, surrounded by slightly developed narrow sclerotized ring, located behind setae Pi. External genital organ almost completely situated in interval between posterior coxal groups.

Genital flaps elongated (ratio length/width = 2.9) with slightly convex lateral margins ( Fig. 4 ). Each genital flap with 11–14 medial and 3–4 lateral thin setae. Two anterior pairs of genital acetabula subequal in size, longer than posterior acetabula.

Trochanter of pedipalp ( Fig. 5 ) very short, without setae. Pedipalpal femur stocky, high, with rather numerous (9–10) thick dorsal setae; ventrodistal portion of femur with large conic projection, bearing one relatively long and two short unequal setae. Genu of pedipalp longer than femur, with two thick and five thin dorsal setae. Pedipalpal tibia slender, longer than genu, slightly curved dorsoventrally, with two very small subequal ventral spines; proximal spine situated near middle of the segment, distal spine in its distal portion. Pedipalpal tarsus ( Fig. 6 ) with large dorsodistal spine with rounded tip, two relatively small ventrodistal pointed spines, very fine dorsal spine, proximal solenidion, one furcated seta and four thin distal ones.

Legs without swimming setae, with relatively few thick and thin short ones ( Fig. 7 ). Genu and tibia of legs III and IV with smooth dorsal setae. Tarsi of all legs slightly thickened distally. Claws with well developed blade (its ventral margin almost straight) and two clawlets of unequal length, external clawlet longer than internal one ( Fig. 8 ).

Measurements (n=1). Length of body 760, width 675; length of anterior dorsal plate 260, width 335; length of posterior dorsal plate 305, width 320; length of coxae I–II 225, width 160; length of coxae III–IV 290, width 215; length of genital flaps 175, width 60; length of genital acetabula (Ac. 1–3): 72, 72, 54; length of pedipalpal segments (P-1–5): 39, 155, 210, 270, 36; length of leg segments: I-L- 1–6 – 75, 110, 125, 205, 210,?; II-L- 1–6 – 75, 125, 135, 225, 235, 200; III-L- 1–6 – 75, 110, 155, 235, 275, 225; IV-L-1–6 –135, 160, 175, 335, 325, 250.

Female. Unknown.

Differential diagnosis. The new species is similar to the African species Sperchon biscutatus Lundblad, 1941 and S. mutatus K.O. Viets, 1981 . Males of these species with two large dorsal plates, covering nearly all surface of the dorsum, the anterior dorsal plate with three pairs of setae, the pedipalpal tibia shorter than the genu, the posterior portion of the ventral surface with large sclerites, bearing posterior setae and free platelets ( Lundblad 1952; Viets 1981). In contrast, in the male S. nevelskoii sp. n. dorsal plates occupy less than half surface of the dorsum, the anterior dorsal plate with one pair of setae, the pedipalpal tibia longer than the genu, the posterior portion of the ventral surface with small sclerites, bearing posterior setae and without free ventral platelets.

Etymology. The new species is named in honour of the Russian Admiral of the Fleet Gennady Ivanovich Nevelskoy, explorer of the Russian Far East.

Habitat. Running waters.

Distribution. Khabarovsk Territory, Far East of Russia.

Figures

FIGURES 1 – 3. Sperchon nevelskoii sp. n., male: 1, idiosoma, dorsal view; 2, fragment of integument; 3, idiosoma, ventral view. Scale bars = 100 μm for Figs. 1, 3; 50 μm for Fig. 2.

FIGURES 4 – 8. Sperchon nevelskoii sp. n., male: 4, genital field; 5, pedipalp; 6, pedipalpal tarsus; 7, leg IV; 8, claw of leg III. Scale bars = 100 μm for Figs. 4, 5, 7; 50 μm for Fig. 8; 25 μm for Fig. 6.