Albaxona (Vietsaxona) similis, Tuzovskij, 2018

Tuzovskij, Petr V., 2018, New water mite species of the genus Albaxona Szalay, 1944 (Acari, Hydrachnidia, Aturidae) from Russia, Zootaxa 4392 (1), pp. 179-195 : 188-192

Albaxona (Vietsaxona) similis sp. n.

( Figs 29–42 )

Type series. Holotype: male, slide 4913- IBIW, Russia, Far East , Primorye Territory , Ussuri National Park, Komarovka River, depth about 0.4 m; substrates: stones, pebbles, sand, 5 July 1984 , Paratypes: 1 male, 29 May 1984, 1 male 17 July 1983, 3 females 29 May 1984 and 1 female 31 May 1984 collected in the same locality as holotype, leg. T.S. Vshivkova. The type material is deposited in the collection of the Papanin Institute for Biology of Inland Waters (Borok, Russia).

Diagnosis. Both sexes: Idiosoma elongate, with straight anterior margin, setae Si and Ci not associated with glandularia, posteriomedial muscle attachment scars on coxal plates IV absent, rostrum short and clearly not reaching anterior capitulum margin, distance between bases of ventral hypostomal setae twice shorter than distance between bases of dorsal setae; excretory pore fused with dorsal shield, glandularia Se free; male: genital field and ventral shield separate, lateral margin of acetabular plates indistinct, gonopore elongate with parallel lateral margins, rounded anterior and posterior ends; female: acetabular plates triangular each with a short posterior projection, posterior genital sclerite lying free, anterior genital sclerite comparatively short and fused with ventral shield.

Description. Both sexes. Idiosoma oval. Dorsal shield covering most of the dorsal surface, bearing 5 pairs of setae: Oi, Oe, Hi, Li, Si ( Fig. 29 ). Setae Oi and Oe located in anterior half of dorsal shield, Hi a little distally to middle of shield, Li in distal portion of shield, and Si very close to posterolateral margins of shield. Setae Si and Ci not associated with glandularia, others idiosomal setae associated with glandularia. Setae Fch, Fp, Vi, Ve, He, Sci, Le, Ci, Pi and four pairs of slit organs (i2–i5) located in the soft interscutal membrane between dorsal and ventral shields: i1 and seta Vi placed on common sclerite on each side, i2 posteriolaterally to Oe, i3 anterior to Sci, i4 posterior to Le, and i5 at level to Si. Setae Fch short, thick and serrate, other idiosomal setae thin, hair–like.

Ventral shield ( Fig. 30 ) broader than dorsal shield, anterior coxal plates projecting beyond anterior margin of idiosoma, suture line between coxal plates II–III distinctly developed only in their lateral parts. Seta Hv located near posterolateral margin of coxal plate II, Ve laterally to coxal plates III, Sce medially to suture line between coxal plates III and IV, glandularia Pe equidistant between insertions of Leg-IV and posterior margin of ventral shield. Аnterior genital sclerite comparatively short (L/W ratio 1.5–2.0), fused with ventral shield. Setae Ci and Pi close to each other and placed on common sclerite caudally on each side. Dorsal and ventral shields porous.

Rostrum short ( Fig. 31 ), clearly not reaching anteriomedial lobes of capitulum; distance between bases of ventral hypostomal setae (h1) twice shorter than distance between bases of dorsal setae (h2), last three times longer than ventral ones. Chelicera with large basal segment and long, thin chela ( Fig. 37 ).

Pedipalp ( Fig. 32 ): P–1 relatively short with single dorsodistal seta; P–2 ventral margin straight, with two subequal dorsoproximal setae and three unequal dorsodistal setae; P–3 with slightly concave ventral margin, 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 (middle seta much longer than the two other setae) and three dorsodistal setae.

Shape and arrangement of setae on legs as shown in figures 38–41. Leg claws ( Fig. 42 ) thin hook–like, with long internal clawlet and short external one, claw lamella not developed.

Male. Dorsal shield elongate (ratio length/width 1.75–1.80). Genital field lying free, lateral margin of acetabular plates indistinct, their anterior margins with two pairs of setae, gonopore elongate with parallel lateral margins and rounded anterior and posterior ends. Ejaculatory complex ( Fig. 33 ) with long anterior arms and comparatively short posterior ones, proximal chamber large with an obtuse angled anterior margin, a pair of short, proximal horns extending to anterior margin of proximal chamber.

Measurements (n=3). Idiosoma L 390–400, W 275–285, dorsal plate L 360–365, W 200–215; genital field L 72–80, W 130–145; genital acetabula (ac.1–3) L: 12–15, 14–15, 13–15;capitulum L 78–84, distance between setae h1-h 1 12–15, distance between setae h2-h 2 25–30; chelicera basal segment L 80–85, chela L 50–53; pedipalpal segments (P-1–5) L: 17–19, 36–45, 30–36, 42–55, 17–19; leg segments L: I-Leg-1–6: 24–30, 41–43, 45–48, 60– 72, 69–73, 69–73; II–Leg-1–6: 30–36, 36–42, 36–42, 45–48, 60–65, 60–70; III–Leg-1–6: 35–42, 36–43, 39–42, 48–55, 60–72, 63–72; IV–Leg-1–6: 90–95, 60–66, 72–80, 75–85, 90–105, 80–95.

Female. Dorsal and ventral shield similar as in male. Аcetabular plates ( Figs 34–35 ) more or less triangular, with five to six fine setae and a short posterior projection. Posterior genital sclerite lying free, anterior genital sclerite moderately long (L/W ratio 2) and fused with ventral shield. Genital acetabula comparatively small, subequal or anterior acetabulum a little smaller than the two posterior acetabula. Glandularium Se situated between anterior margin of genital plate and posterior margin of coxal shield.

Measurements (n=4). Idiosoma L 385–420, W 280–300; dorsal plate L 360–390, W 210–245; acetabular plate L 65–75, W 30–36; genital acetabula (ac.1–3) L: 12–15, 15–20, 15–20; capitulum L 75–80, distance between setae h1-h 1 14–16, distance between setae h2-h2 75–80; chelicera: basal segment L 85–90, chela L 50–55; pedipalpal segments (P1–5) L: 18–20, 42–46, 27–30, 50–55, 20–24; leg segments L: I-Leg-1–6: 30–35, 30–35, 42–48, 65–70, 65–72, 57–65; II–Leg-1–6: 30–35, 30–35, 35–37, 42–48, 57–60, 60–65; III–Leg-1–6: 35–42, 36–42, 35–42, 48– 55, 65–72, 65–72; IV–Leg-1–6: 72–90, 50–60, 65–70, 72–78, 84–90, 75–85.

Differential diagnosis. The present species is closely related to Albaxona intermedia Tuzovskij, 1986 described from Primorye Territory also ( Tuzovskij1986). The male and female of A. similis sp. n. differ from the adult of A. intermedia mainly by the structure of the capitulum and the genital area. The rostrum of A. intermedia is long, reaching or slightly extending to anterior margin of the capitulum, the distance between the bases of ventral and dorsal hypostomal setae is subequal ( Fig. 36 ), the male gonopore is pointed anteriorly and expanded posteriorly ( Fig. 43 ) and the female glandularium Se is situated laterally to the anterior margin of the acetabular plate ( Tuzovskij 1986). The genital field of the male A. intermedia differs slightly from the original illustration in Tuzovskij (1986), probably as a result of fixing in formalin. In contrast, the rostrum of A. similis sp. n. is short and clearly not reaching the anteriomedial lobes of the capitulum ( Fig. 31 ), the distance between the bases of ventral hypostomal setae (h1) is twice smaller than the distance between the bases of the dorsal setae (h2); the male gonopore has parallel lateral margins and is rounded anteriorly ( Fig. 30 ), the female glandularium Se is situated between the anterior margin of the acetabular plate and posterior margin of the coxal shield ( Fig. 34 ).

Etymology. The Latin “ similis ” means similar. The morphology of the new species is similar to Albaxona intermedia .

Habitat. Running waters.

Distribution. Аsia ( Russia, Primorye Territory).

Figures

FIGURES 29–30. Albaxona similis sp. n., male: 29, dorsal view; 30, ventral view. Scale bar: 100 µm.

FIGURES 31–36. Albaxona similis sp. n. and A. intermedia Tuzovskij, 1986: 31, 36, capitulum, ventral view; 32, pedipalp; 33, ejaculatory complex; 34, idiosoma, ventral view; 35, acetabular plate; 31–33, 36, male; 34–35, female; 31–35, A. similis sp.n.; 36, A. intermedia. Scale bars: 31, 33, 35–36 = 50µm; 32 = 20 µm; 34 = 100 µm.

FIGURES 37–43. Albaxona similis sp. n., male and A. intermedia Tuzovskij, 1986, male: 37, chelicera; 38, Leg I; 39, Leg II; 40, Leg III; 41, Leg-IV; 42, claw of leg IV; 43, posterior part of ventral view; 37–42, A. similis sp. n.; 43, A. intermedia. Scale bars: 37, 38–41 =50 µm; 42 = 20µm; 43 = 100µm.