Water mites of the genus Atractides Koch, 1837 from Kyrgyzstan (Acari: Hydrachnidia: Hygrobatidae) with the description of six new species

Water mites of the genus Atractides Koch, 1837 are among the most frequently found mites in running waters of the Western Palaearctic. In the present study, new records are given for two previously described species, and six species new to science are described from Kyrgyzstan, i.e., Atractides bellus n. sp., A. karakali n. sp., A. kyrgyzicus n. sp., A. tienshanensis n. sp., A. ivanae n. sp. and A. yunusi n. sp. All material was collected in August 2013 during a collecting trip of the authors.


Introduction
Water mites of the genus Atractides Koch, 1837 have been found in all biogeographical regions except Antarctica and Australasia. The most recent checklist of species of the genus was published by Pešić & Smit (2011), listing 297 species worldwide, most of them reported from the Palaearctic (138 spp., around 46%), mostly from the Western Palaearctic and the countries surrounding the Mediterranean Sea. Since then a plethora of publications with descriptions of new Atractides species from the Palaearctic has been published (Cichocka and Biesadka 2013; Gerecke and Di Sabatino 2013; Gülle et al. 2015; Pešić et al. 2012a, b, 2014, 2020; Pešić and Smit 2018, Tuzovskij 2011, 2013, 2014 increasing the number of known species from the latter region to 164. In the Palaearctic, the species of the genus Atractides are among the most frequently collected mites in running waters, as well as in springs and interstitial waters. In the latter region, the genus comprises three subgenera, i.e. Atractides s. s., Tympanomegapus Thor, 1923, andPolymegapus K. Viets, 1926. So far only four species, Atractides (Polymegapus) grigorievka Pešić & Smit, 2018, A. (Atractides) alaarchaensis  sonkulensis  manasi  were known from Kyrgyzstan, all described on the basis of material collected by the authors during a collecting trip from 1 to 15 August 2013 to Kyrgyzstan. In this paper, six further new species of the genus are described. The number of water mites species of Kyrgyzstan now tallies 43 species .  smooth; Vgl-1 not fused to Vgl-2; P-3 with one seta on medial surface; male P-2 ventral margin without a projection, P-3 with a small, lamellar extension in the centre.
Etymology -Named for being a beautiful species.
Discussion -The combination of a characteristically shaped Cx-I+II plate (caudally protruding forming a large and irregular, a mace-like mediocaudal extension) and palp (P-3 with one seta on medial surface, in male P-3 with a small, ventral extension in distal half) is unique and separates the new species from all other members of the genus.
Distribution -Kyrgyzstan; so far only known from one spring (see Fig 18B in Pešić and Smit 2020) in Tien Shan mountains at an elevation of about 3,300 meters.
Etymology -Named after the country where the new species was found.
Discussion -The new species resembles Atractides tienshanensis n. sp. (for similarities and differences see below in discussion of the latter species). In the key of Western Palaearctic species provided by Gerecke (2003) the new species is placed close to A. neumani (Lundblad, 1962), a rhitrobiontic species known from Sweden and Poland (Gerecke et al. 2016). The latter species can easily be separated in male by a smaller dimensions of I-L and palp (L I-L-5/6 ˂170/130, P-4 ˂ 100 µm), a genital plate being wider than long, and a more slender and homoimorphic sword setae of I-L-5 (Gerecke 2003).
Etymology -The new species is named after the Tien Shan mountain range from where the new species originates.
Discussion -Due to a similar shape of the palp (male P-2 ventrodistal margin convexly protruding) and a moderate interspace (˂ 20 in ♂, ˂ 30 µm in ♀) between the sword setae of I-L-5, the new species resembles A. kyrgyzicus n. sp. (see above). From the latter species A. tienshanensis n. sp. can be separated in the male by the genital plate being wider than long (longer than wide in A. kyrgyzicus n. sp..; compare figures 6A-B with figures 9A, 10A), a P-2 ventrodistal margin with a rugose surface, a comparatively short ventral setae of P-4 and a stouter I-L-6 (dL/H ˂ 5.0 vs. ˃ 5.0 in A. kyrgyzicus n. sp. ).
In the key of Western Palaearctic species provided by Gerecke (2003) the new species were placed close to A. glandulosus (Walter, 1918). The latter species in the both sexes differ in more enlarged dorsal glandularia (diameter ˃ 30 µm) and I-L-5 more thickened in its distal part (ratio dL/H 2.6-3.0, data taken from Smit et al. 2015), and in the male by very strong and long sword seta on P-4, inserting slightly anterior to proximoventral seta (Smit et al. 2015).
Atractides issajewi (Sokolow, 1928) from Uzbekistan, a species known only in the male sex, is similar in having a slightly protruding ventral margin of P-2 but differs in the P-4 with the sword seta inserting near proximoventral seta, and by a higher number of setae on the lateral margin of the genital plate (Sokolow 1940).
Etymology -The new species is named after Ivana Pozojević (Zagreb, Croatia) in appreciation of her work on water mites.
Discussion -The presence of a strong ventral protrusion on P-3 in males, makes the new species similar to A. gibberipalpis Piersig, 1898, A. inflatus (Walter, 1925 and A. yunusi n. sp. (see below). Atractides gibberipalpis, a rhitrobiontic species from the Palaearctic (Sokolow 1940, Gerecke 2003, Pešić et al. 2004, Pešić and Erman 2006 differs from both new species from Kyrgyzstan in the shape of male genital plate (Ac larger, Ac-3 elongated, drop-shaped, anterior margin more or less indented; see Figure 13D). Atractides inflatus differs in having lineated integument, in the both sexes I-L-6 relatively long, L I-L-5/6 ratio 1.3-1.4, in male the protrusions of P-2 and -3 more laterally flattened, and in female the both P-2 and P-3 with a gentle central thickening covered by fine denticulation (Gerecke 2003). For similarities and differences in comparison with Atractides yunusi, see below in discussion of the latter species.
Distribution -Kyrgyzstan; know from the high-order streams in Tien Shan mountains at an elevation from 2,400 to 3,400 meters.
Description -General features -Integument striated, muscle insertions unsclerotized; mediocaudal margin Cx-I convex, apodemes of Cx-II in an acute angle with the median line. Ac in a weakly cuved line, subtriangular in shape. Excretory pore smooth; Vgl-1 not fused to Vgl-2. Palp with strong sexual dimorphism, P-4 sword seta nearer to distoventral seta. I-L-5 setae S-1 and S-2 separated, S-1 longish with truncate tip, S-2 proximally enlarged; I-L-6 long and slender, curved, proximally slightly thickened, with parallel dorsal and ventral margins from the centre to the claw pit ( Figure 13D). Male -Genital plate anterior margin slightly convex, posterior margin indented ( Figure 13B); P-2 and P-3 each with a distinct ventral extension, P-4 slightly protruding near proximoventral seta, length of ventral setae not exceeding the length of the segment ( Figure 13E). Female -genital plates medial margin with concavity on the level of Ac-2; ventral margin of P-2 stright, slightly convex at distal edge; P-2 and P-3 without projections, ventral margins of P-3 and P-4 straight ( Figure 14B).
Etymology -The new species is named after Yunus Esen (Bingöl, Turkey) in appreciation of his scientific work on water mites.
Discussion -Due to a similar shape of the palp and genital field, the new species most closely resembles A. ivanae n. sp. (see above). From the latter species, Atractides yunusi n. sp. differs in both sexes in the more slender I-L-6 (dL/H > 6.0), S-1 apically truncated, and in males ventral setae of P-4 is shorter, not exceeding the length of the segment as in A. ivanae n. sp.
Distribution -Kyrgyzstan; known from high-order streams in Tien Shan mountains at an elevation from 2,700 to 3,400 meters.
Key to the species of the genus Atractides of Kyrgyzstan