Limnesia (Limnesia) vietnamensis, Tuzovskij, Petr V., 2013

Tuzovskij, Petr V., 2013, New water mite species (Acari, Hydrachnidia) from Vietnam, Zootaxa 3700 (4), pp. 547-560 : 550-554

Genus Limnesia Koch, 1836

Limnesia (Limnesia) vietnamensis , sp. n. ( Figs 8–17 )

Holotype: female, slide 9694, 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 a.s.l., 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). Paratype: one deutonymph, slide 9695, from the same locality and collection date as holotype.

Diagnosis. Female: dorsum with two very small anterior sclerites bearing setae Oi and with a small posterior transverse platelet, P-3 with four setae, distance between anterior and median genital acetabula considerably longer than one half of median acetabulum, ratio L subterminal seta to L IV—Leg-6, 0.7. Deutonymph: acetabular plate trapezoidal, posterior acetabula larger than anterior ones, distance between anterior and posterior acetabulum less than the diameter of the anterior acetabulum; ratio L subterminal setae to L IV—Leg-6, 0.8.

Description. Female. Idiosoma oval, integument soft and smooth. The number and position of idiosomal setae typical for the genus Limnesia . All dorsal setae thin and approximately equal in length, but setae Fch ( Fig. 8 ) thicker than other idiosomal setae associated with glandularia, trichobothria and setae Pi. Dorsum with two very small anterior sclerites bearing setae Oi and with a small posterior platelet.

Coxae of legs ( Fig. 9 ) cover about half the ventral surface. Medial margins of first coxae well developed, straight, separated medially, apodemes short. Coxal plates III+IV triangular, suture line of these coxae complete. Setae Pe and associated glandularia clearly separated, setae Pe located medially of associated glandularia. External genital area with three pairs of acetabula, located between posterior coxal groups. Genital flaps elongate (L/W ratio 2.6), with 12-13 thin setae ( Fig. 10 ). First pair of genital acetabula noticeably separated from second and third pairs, posterior two pairs situated close to each other, second pair lying lateral to third pair.

Capitulum ( Fig. 11 ) with almost straight ventral margin, dorsodistal projections long, both pairs of hypostomal setae subequal. Chelicera with large basal segment and relatively short claw.

Pedipalp ( Fig. 12 ) slender; P-1 short, without setae; P-2 large, with five short unequal dorsal setae, ventral margin concave with distal protrusion bearing a peg-like seta; P-3 with four setae; P-4 slender, with two very small tubercles bearing two unequal setae and two short solenidia, proximal seta shorter than distal one.

Legs I without swimming setae; legs II–IV with swimming setae, their number as follows: 1 on II—Leg-3 and on III—Leg-3, 4 on III—Leg-4, 8 on III—Leg-5, 6 on IV—Leg-4 and 6–7 on III—Leg-5. IV—Leg-6 with four thick unequal setae, ratio L subterminal seta to L IV—Leg-6, 0.7 ( Fig. 13 ). Claws of legs I–III with large median and short, thin dorsal and ventral clawlets ( Fig. 14 ).

Measurements (n=1). Idiosoma L 750; coxal field L 315, W 560; posterior dorsal plate L 36, W 48; capitulum L 108; chelicera L 170, cheliceral claw L 50; pedipalpal segments (P-1–5) L: 18, 72, 73, 108, 27; genital flaps L 125, W 48; genital acetabula (ac.1–ac.3) L/W: 49/24, 30/18, 36/27; L of leg segments: I—Leg-1–6: 42, 65, 63, 72, 90, 95; II—Leg-1–6: 42, 72, 75, 90, 115, 113; III—Leg-1–6: 60, 65, 70, 108, 125, 108; IV—Leg-1–6: 115, 85, 105, 140, 145, 130; subterminal setae on IV—Leg-6 L 90.

Deutonymph. Idiosoma as in female, but coxal plates with a smaller number of setae ( Fig. 15 ). Suture line between coxal plates III and IV oblique and complete. Acetabular plate trapezoidal, with two pairs of acetabula and three pairs of setae; posterior acetabula larger than anterior ones, distance between anterior and posterior acetabulum less than the diameter of the anterior acetabulum. Excretory pore located anterior to setae Ci.

Pedipalp ( Fig. 16 ) slender: P-1 short, without seta; P-2 large, with concave ventral margin and small ventrodistal protrusion, bearing three subequal dorsal setae; P-3 with two subequal dorsal setae, base of proximal seta located near the middle of the segment; P-4 long, ventral setae located on very small subequal tubercles near the middle of segment, proximal seta shorter than posterior one.

Legs thin and slender. Legs III–IV with long swimming setae ( Fig. 17 ), with the following numbers: 1 seta on III—Leg-4 and IV—Leg-4, 2 setae on III—Leg-5 and IV—Leg-5; ratio L subterminal setae to L IV—Leg-6, 0.8.

Measurements (n=1). Idiosoma L 385; coxal area L 180, W 330; capitulum L 65; chelicera L 115, cheliceral claw L 42; pedipalpal segments (P-1–5) L: 12, 45, 42, 66, 22; genital plate L 48, W 75; L/W genital acetabula (ac.1–2): 21/16, 24/18; L of leg segments: I—Leg-1–6: 27, 42, 35, 45, 55, 65; II—Leg-1–6: 30, 42, 42, 55, 69, 75; III—Leg-1–6: 40, 35, 36, 55, 70, 78; IV—Leg-1–6: 63, 42, 55, 78, 85, 85; terminal setae on IV—Leg-6 L 72.

Remarks. The present species is similar to Limnesia isensis Imamura, 1965 , L. koenikei Piersig, 1894 , L. caucasica Tuzovskij, 1997 and L. neokoenikei Jin, 1997 . All these species have a P-2 with a ventrodistal protrusion bearing a peg-like seta. The new species differs from L. isensis in the following characters (character states of female L. isensis are indicated in parenthesis from Imamura 1965): the posterior dorsal plate transverse, L/W ratio 0.85 (elongate, L/W ratio 1.2), the distance between anterior and median genital acetabula considerably longer than one half of median acetabulum (lesser than one half of median acetabulum) and a peg-like seta of P-2 relatively stout (peg-like seta of P-2 thin). The dorsum in adults and deutonymphs of L. koenikei and L. caucasica bearing two posterior platelets (Tuzovskij 1997, 2004), while in female and deutonymph of L. vietnamensis sp.n. the dorsum has a single posterior platelet. The dorsum in adults of L. neokoenikei is without posterior platelet(s), the first and second acetabula in the female are close to each other on each side and IV–Leg-6 has three short thick setae (Jin 1997); in contrast, the dorsum in female and deutonymph of L. vietnamensis sp.n. has a posterior platelet, the first and the second acetabula in the female are well separated and IV–Leg-6 bearing four short thick setae. Etymology. The species is named after the country where it was collected ( Vietnam). Habitat. Running waters.

Distribution. Asia ( Vietnam: Dong Nai Province).

Figures

FIGURES 8 – 10. Limnesia vietnamensis sp. n. female: 8, dorsal view; 9, coxal plates and genital field; 10, genital field. Scale bars: 8, 9 = 100 Μm; 10 = 50 Μm.

FIGURES 11 – 14. Limnesia vietnamensis sp. n. female: 11, capitulum and chelicera, lateral view; 12, pedipalp, lateral view; 13, genu, tibia and tarsus of leg IV; 14, claws of leg I. Scale bars: 11, 12 = 50 Μm; 13 = 100 Μm; 14 = 20 Μm.

FIGURES 15 – 17. Limnesia vietnamensis sp. n. deutonymph: 15, idiosoma, ventral view; 16, pedipalp; 17, genu, tibia and tarsus of leg IV. Scale bars: 15 = 100 Μm; 16 = 20 Μm; 17 = 50 Μm.