Hygrobates kirgizicus Sokolow, 1935

Pešić, Vladimir & Smit, Harry, 2021, New records of the water mite genus Hygrobates Koch, 1877 from Kyrgyzstan (Acari, Hydrachnidia, Hygrobatidae), with the description of one new species, Ecologica Montenegrina 39, pp. 7-14 : 8-10

Hygrobates kirgizicus Sokolow, 1935

Figs. 1-2

Material examined — Kyrgyzstan: KR26 Kochkor region , rheocrenes + slow flowing stream, along road Kochkor-Balysky, 42º16.391' N, 75º51.204' E, 1761 m asl., 15.viii.2013 leg. Pešić & Smit, 24/21/2 (2/1/0 dissected and slide mounted) .

Morphology — Both sexes: Integument finely striated; dorsal and ventrocaudal idiosoma without sclerotized muscle insertions. Posteromedial margin of Cx-I+II parabola-shaped. Cx-IV sub-triangular, with anterior and posterior margins converging towards the median line ( Figs. 1 A-B). Acetabula rounded, in triangular arrangement. P-2 distoventrally protruding in a short, rounded projection covered by small denticles, P-3 with denticles covering distal two thirds of ventral margin, P-4 slightly protruding near ventral setae insertions ( Figs. 1 F-G). IV-L-6 proximoventral seta similar in size to distoventral one ( Fig. 2A ), L 7-8 µm. Male: Anterior margin of genital field convex with a small knob- shaped medial projection, posterior margin indented, with a medial protrusion ( Figs. 1 C-D). Female: Medial margin of the genital plate indented in the centre.

Measurements. Male (n=1) — Idiosoma: L 975, W 800; coxal field: L 453; Cx-III W 575; mL of CxI + gnathosoma L 377; distance between lateralmost ends of Cx-II apodemes, 175; genital field L/W 225/181, ratio 1,24; L Ac-1-3: 61-66, 69, 70-75. Ejaculatory complex ( Fig. 3E ) 163.

Palp – total L 509; dL/H, dL/H ratio: P-1, 38/47, 0.82; P-2, 144/88, 1.64; P-3, 97/73, 1.33; P-4, 167/43 [basal 42], 3.9 [4.0]; P-5, 63/23, 2.75; P-2/P-4 ratio 0.86. Chelicera total L 381, L basal segment 247, claw 140, L ratio basal segment/claw 1.8.

Legs – dL of I-L-1-6: 88, 103, 134, 200, 205, 216. dL of IV-L-1-6: 156, 159, 241, 341, 341, 312.

Female (n=1) — Idiosoma: L 950, W 750; coxal field: L 478; Cx-III W 641; mL of Cx-I + gnathosoma L 409; distance between lateralmost ends of Cx-II apodemes, 213; genital field L/W 216/291; genital plate L 184-199; gonopore L 188; L gonopore/genital plate ratio 0.95-1.02; L Ac-1-3: 72-77, 75-83, 53-63.

Palp – total L 565; dL/H, dL/H ratio: P-1, 45/55, 0.82; P-2, 155/97, 1.6; P-3, 106/83, 1.28; P-4, 188/50[basal 47], 3.75 [4.0]; P-5, 71/25, 2.8; P-2/P-4 ratio 0.83. Chelicera total L 500, L basal segment 350, claw 153, L ratio basal segment/claw 2.3.

Legs – dL of I-L-1-6: 88, 116, 153, 225, 234, 234. dL of IV-L-1-6: 178, 183, 275, 375, 381, 350.

Remarks — Considering the morphology of palp and genital field, the specimens reported here agree with Hygrobates kirgizicus Sokolow, 1935 , originally described from a tributary of the Chui River in the Ortotokoy valley, Kazakhstan (Tian Shian Mountains) at altitudes of 1700-1800 m. In addition, Sokolow (1935) reported the species from a depth of 10 m in Nizhneye Mul’tinskoye Lake (Altai, 1700 m asl, Russia).

In regard to the shape of palp and idiosoma, H. kirgizicus is most similar to H. longipalpis (Hermann, 1804) . For a long time, the latter had been considered a species with a Holarctic distribution, but a recent study conducted by Pešić et al. (2019) revealed within H. longipalpis the presence of two distinct lineages, with H. prosiliens Koenike, 1915 , for a long time considered its junior synonym and now reestablished, having a preference for standing waters, and H. longipalpis s. str. inhabiting slow flowing sectors of running waters. From both species, H. kirgizicus can be separated in Cx-IV sub-triangular in shape, with anterior and posterior margins converging towards the median line.

Distribution — Kazakhstan, Russia (Altai) ( Sokolow 1935); Kyrgyzstan (this study).

Figures

Figure 1. Photographs of Hygrobates kirgizicus Sokolow, 1935 (A, C-E, G – male; B, F – female): A-B – coxal and genital field; C-D – genital field; E – ejaculatory complex; F-G – palp.

Figure 2. Hygrobates kirgizicus Sokolow, 1935, male: A – IV-L-5 and -6 (arrows indicate ventral setae, 2X); B – palp. Scale bars = 100 µm.

Figure 3. Hygrobates tienshanensis sp. nov., holotype male: A – idiosoma, ventral view; B – genital field; C-D – palp; E – I-leg. Scale bars = 100 µm.