Hygrobates (Hygrobates) caucasicus, Tuzovskij, 2021

Tuzovskij, Petr V., 2021, A new water mite species of the Hygrobates fluviatilis-complex from Russia (Acari Hydrachnidia, Hygrobatidae), Zootaxa 4974 (1), pp. 193-196 : 193-196

Hygrobates (Hygrobates) caucasicus sp. n.

( Figs 1–9 )

Material examined. Holotype female (slide 1698a), Russia, North Caucasus , Krasnodarsky Kray , Ubin stream, near settlement Ubinskaya, 27.05.1976, leg. Tuzovskij. Paratypes: one male and one female, 18 May 1976 in the same locality as holotype .

Diagnosis. Membranous integument dorsally and ventrally finely striated; anterior coxal groups with short apodemes; posteromedial margin of coxal plates I convex to angular and without subcutaneous extension, coxal plate IV subrectangular; P-2 ventrodistal projection rather long, denticulation restricted on it ventral surface only, P-3 ventral margin convex distally.

Description. Both sexes. Colour yellow-grey. Idiosoma oval and somewhat flattened dorsoventrally. Integument dorsally and ventrally finely striated. Setae Fch ( Fig. 1 ) moderately long and much thicker than other idiosomal setae. Anterior coxal group with short apodemes, posteromedial margin of coxal plates I convex to angular and without subcutaneous median extension ( Fig. 2 ). Coxal plate IV subrectangular, with a nose-like protruding medial margin. Excretory pore unsclerotized, located between flanking glandularia (Ci).

Chelicera ( Fig. 5 ) with large basal segment and relatively small sickle-shaped chela. Pedipalp ( Fig. 6 ) moderately long; P-1 with single dorsodistal seta; P-2 with six short, thick dorsal setae, ventral margin slightly concave and without denticulation, distally protruding in a long projection covering by a few denticles; P-3 with two short, thick dorsoproximal, two comparatively thin dorsodistal subequal setae and three to five thin setae, ventral margin distally slightly convex, with a few small denticles covering distal two thirds of ventral surface; P-4 slender with slightly concave ventral margin, both ventral setae located in distal half of segment (separation 48–55 μm).

Legs slender, without swimming setae. I/II-Leg-4–5 with two subequal relatively long, thick pointed distoventral setae ( Fig. 7 ); IV-Leg-4 with five (two long and three short) thick distal setae, IV-Leg-5 with four short, thick unequal distal setae ( Fig. 8 ).Claws of all legs with long external clawlet and short internal one, lamella with concave ventral margin( Fig. 9 ).

Female. Acetabular plates ( Fig. 3 ) triangular (L/W ratio 1.37–1.75), as long as gonopore, with 14–17 pairs thin setae, three pairs of them considerably longer than other genital setae. Medial margin of acetabular plate slightly indented near the center; acetabula in triangular arrangement, ac-2 and ac-3 on the same level or ac-2 a little shifted anteriorly. Anterior genital sclerite a little larger than posterior one.

Measurements (n=2). Idiosoma L 650–1000; coxal plates I+capitulum mL 305–315; genital plates L 130–155, W 72–90, genital acetabula (ac-1–3) L/W 48–70/36–42, 65–85/24–42, 60–78/36–42; cheliceral segments L: base 245–250, chela 95–102; pedipalp segments (P–1–5) L: 30–36, 125–145, 105–120, 180–210, 48–54; legs segments L: I-Leg-1–6: 65–80, 95–100, 95–115, 150–185, 155–195, 145–165; II-Leg-1–6: 65–85, 95–100, 130–140, 145–205, 180–225, 160–190; III-Leg-1–6: 65–72, 85–95,125–140, 195–210, 210–225, 180–190; IV-Leg-1–6: 120–135, 125–140, 155–185, 230–280, 255–300, 220–260.

Male. Genital plate ( Fig. 4 ) wider than long, anterior margin with a small, knob-shaped projection, posterior margin deeply indented without median protrusion, with 20–23 pairs of setae; acetabula in a triangular arrangement, ac-2 and ac-3 on the same level.

Measurements (n=1). Idiosoma L 810; coxal plates I + capitulum mL 305; genital plate L 150, W 180, genital acetabula (ac-1–3) L/W 65/36, 72/36, 54/30; cheliceral segments L: base 210, chela 90; pedipalp segments (P–1–5) L: 30, 120, 96, 175, 48; legs segments L: I-Leg-1–6: 65, 78, 100, 160,165, 140; II-Leg-1–6: 70, 80, 115, 180, 200, 160; III-Leg-1–6: 80, 85, 125, 125, 240, 185; IV-Leg-1–6: 125, 125, 170, 250, 280, 220.

Remarks. The present species is similar to Hygrobates fluviatilis . Differences are found in the following characters (character states of Hygrobates fluviatilis given in parentheses, data from Pešić et al. 2017): membranous integument dorsally and ventrally finely striated (reticulated), coxal plate IV subrectangular (subtriangular), P-2 denticulation restricted on the ventral surface of the distoventral projection only (well developed denticulation covering the distoventral projection and extending to the more proximal part of the ventral surface), P-3 with denticles covering distal half of ventral surface (distal two thirds of ventral surface), male posterior margin of the genital field deeply indented without a protrusion in the centre of indentation (with protrusion).

Larva, deutonymph. Unknown.

Etymology. The species is named after the Caucasus region where it was collected.

Distrbution. Europea, Russia: Krasnodar Territory.

Habitat. Running waters.

Figures

FIGURES 1–5. Hygrobates caucasicus sp. n., adults: 1, seta Fch; 2, ventral view; 3–4, genital field of female; 5, chelicera; 1–3, 5, female; 4, male. Scale bars: 1= 50 μm, 2 = 200 μm, 3–5 = 100 μm.

FIGURES 6–9. Hygrobates caucasicus sp. n., female: 6, pedipalp; 7, I-Leg-4–6; 8, IV-Leg-4–6, 9, leg claw. Scale bars: 6, 9 = 50 μm; 7–8 = 100 μm.