Albaxona gusevi Tuzovskij

Tuzovskij, Petr V., 2013, New water mite species (Acari, Hydrachnidia) from Vietnam, Zootaxa 3700 (4), pp. 547-560 : 556-559

Genus Albaxona Szalay, 1944

Albaxona gusevi Tuzovskij , sp. n. ( Figs 24–33 )

Holotype: female, slide 9520, Vietnam, Khanh Hoa Province, Khế River near the inflow of Cai River (N 12°16.741’, E 108°54.669’), 0 2. 0 6. 2008 (leg. E.S. Gusev). The river bottom is dominated by pebbles and sand, depth 1.0 m, speed of current 0.8 m/s, pH 7.8.

Diagnosis. Female: dorsal shield elongate, L/W ratio 1.8; excretory pore is shifted far away from the posterior margin of the dorsal shield, I-Leg-6 distinctly tapering distally.

Description. Female. Idiosoma oval, compressed dorso-ventrally, dorsal and ventral shields present. Dorsal shield elongate, L/W ratio 1.8, covering nearly the complete dorsal surface and with five pairs of setae: Oi, Oe, Hi, Li, Si ( Fig. 24 ). Setae Oi and Oe located in anterior half of dorsal shield, Hi near middle of shield, Li in distal portion of shield, and Si very close to posterolateral margins of shield. Setae Fp, Oi, Si, Ci and Pi without glandularia, other idiosomal setae associated with glandularia. Setae Fch, Fp, Vi, Ve, He, Sci, Le, Ci, Pi and all slit organs (i1–i5) located on soft interscutal membrane between dorsal and ventral shields: i1 and seta Vi placed on common sclerite on each side, i2 at level and laterally to Oe, i 3 anteriorly to Sci, i4 posterior to Le, and i5 laterally to Si. Excretory pore near distal end of dorsal shield.

Ventral shield ( Fig. 25 ) broader than dorsal shield, anterior coxal plates projecting beyond anterior idiosoma margin, suture line between coxal plates II–III well developed only on their lateral parts. Setae Hv located near lateral margin of coxal plates II, Ve laterally to coxal plates III, Sce medially to suture line between coxal plates III and IV, Pe more or less equidistant from insertion of leg IV and posterior end of coxal shield, Se on soft integument between posterior margin of coxal shield and genital plates. Setae Ci and Pi close to each other and lying on a common sclerite. Dorsal and ventral shields punctate. Acetabular plates narrowed posteriorly, longer than wide (L/ W ratio 2.8), with relatively wide rounded anterior margin, with three acetabula (located in an arc line) and four to five fine setae each; all acetabula small and more or less oval, but posterior acetabulum a little smaller than anterior acetabula.

Capitulum ( Fig. 26 ) with a short rostrum, without anchoral processes, dorsal hypostomal setae longer and thicker than ventral hypostomal setae. Chelicerae with a large basal segment and a long, thin claw ( Fig. 27 ). Pedipalps moderately slender ( Fig. 28 ): P-1 relatively short with single dorsodistal seta; P-2 with straight ventral margin, with two subequal dorsoproximal setae and three unequal dorsosodistal setae; P-3 with slightly concave ventral margin, with two dorsoproximal and two dorsodistal subequal setae, all these setae considerably shorter than dorsal margin of segment; P-4 slender, with three rather long unequal ventral setae near middle of segment.

Shape and arrangement of setae on leg segments as shown in Figs 29–32 . All legs without swimming setae. First legs ( Fig. 29 ) longer than second legs ( Fig. 30 ). I—Leg-6 tapering distally. Leg claws ( Fig. 33 ) thin hook– like, with long internal denticle and short external spur, claw lamella not developed.

Measurements (n=1). Idiosoma L 290, W 210; dorsal shield L 240, W 130; genital plate L 50, W 18; genital acetabula (ac. 1–3) L/W: 6.5/16, 9.6/18, 9.5/8; capitulum L 70; chelicera L 130, cheliceral claw L 39; pedipalpal segments (P-1–5) L: 218, 36, 25, 42, 15; L of leg segments I—Leg.1–6: 18, 24, 35, 54, 60, 48; II—Leg.1–6: 24, 24, 27, 36, 40, 42; III—Leg.1–6: 24, 36, 27, 36, 45, 46; IV—Leg. 1–6: 60, 40, 48, 54, 60, 60.

Remarks. The present species is similar to Albaxona stoka Cook, 1967 , A. nearctica Cook, 1974 , A. intermedia Tuzovskij, 1986 and A. indica Pesic & Ranga Reddy, 2009 . All these species well differ from the female of A. gusevi sp. n. by the arrangement of the excretory pore. The excretory pore in adults of A. stoka and A. indica is lying in the soft integument (Cook 1967 and Pesic & Ranga Reddy 2009, respectively), while in the female of A.gusevi sp. n. the excretory pore is fused with the dorsal shield. The excretory pore in adults of A. nearctica and A. intermedia opens on the posterior margin of the dorsal shield and I—Leg-6 is identical in thickness on the whole length (Cook 1974 and Tuzovskij 1986, respectively). In contrast, in the female of A. gusevi sp. n. the excretory pore is shifted far away from the posterior margin of the dorsal shield ( Fig. 24 ) and I–Leg-6 is distinctly tapering distally ( Fig. 29 ).

Etymology. The species is named after Dr. Eugeny Gusev.

Habitat. Running waters.

Distribution. Asia ( Vietnam, Khanh Hoa Province).

Figures

FIGURES 24 – 25. Albaxona gusevi sp. n. female: 24, dorsal view; 25, ventral view. Scale bar: 50 Μm.

FIGURES 26 – 28. Albaxona gusevi sp. n. female: 24, capitulum, ventral view; 25, chelicera, lateral view; 28, pedipalp, lateral view. Scale bars: 26, 27 = 50 Μm; 28 = 20 Μm.

FIGURES 29 – 33. Albaxona gusevi sp. n. female: 29, leg I; 30, leg II; 31, leg III; 32, leg IV; 33, claw of leg I. Scale bars: 29 - 32 = 50 Μm; 33 = 100 Μm.