New records of the water mite genus Atractides Koch, 1837 from Iran (Acari: Hydrachnidia: Hygrobatidae)

In the present study three water mite species of the genus Atractides Koch, 1837 are reported from Iran. Atractides yazdensis sp. nov ., is decribed as new for science; the hitherto unknown females of A. elburzensis Pešić, Smit & Saboori, 2014 and A. bakhtiari Pešić, Asadi & Saboori, 2016 are described.


Introduction
The water mite genus Atractides Koch, 1837 has been found in all biogeographical regions except Antarctica and Australasia (Gerecke 2003). The name Atractides was firstly proposed in 1837 by the German arachnologist Carl Ludwig Koch, with A. spinipes Koch, 1837 as typus generis (Radford 1950). In the Palaearctic, the genus comprises of three subgenera, i.e., Atractides s. s., Tympanomegapus Thor, 1923, andPolymegapus K. Viets, 1926. More than 180 years of taxonomic studies has led to the identification of 172 species from the Palaearctic region (Pešić and Smit 2021a, b).
In this paper, one new species of the genus Atractides is described from Iran. Moreover, the hitherto unknown females of two species (A. elburzensis and A. bakhtiari) are described.

Material and Methods
Water mites were collected by hand netting, sorted live in the field, and immediately preserved in Koenike's fluid and/or 96% ethanol. Some specimens were dissected, and slide mounted in Faure's medium. Morphological nomenclature follows Gerecke et al. (2016). The holotype and paratype of the new species are deposited in Naturalis Biodiversity Center in Leiden (RMNH). In the section 'Material examined' collecting site abbreviations derive from the geographical database Pešić.
Remarks -The species was described by Pešić et al. (2014) on the basis of a single male collected in a mountain stream in Kheirud Kenar forest in Mazandaran Province. Therefore, this is the first description of the female.
Remarks -The species was described by Pešić et al. (2016) on the basis of a single male collected in a small stream in Chahar Mahal and Bakhtiari Province. The latter specimen was originally assigned by Pešić et al. (2004a) to A. fluviatilis, a species which in both sexes differs in the shape of the genital field and arrangement of Ac (A. fluviatilis: Ac nearly equal or Ac-3 larger, male genital plate anterior margin straight or slightly concave). This is the first description of the female.
The new record of A. bakhtiari from the northern Khorasan province is about 1000 kilometers away from the locus typicus of the latter species (Fig. 4), and therefore additional studies relying on molecular analysis are recommended.
Description. Male -Integument striated, muscle insertions unsclerotized; mediocaudal margin Cx-I slightly concave, apodemes of Cx-II in an acute angle with the median line. Genital plate anterior margin straight or slightly concave, posterior margin indented, Ac in an obtuse triangle, subtriangular in shape (Figs. 5D-E). Excretory pore smooth; Vgl-1 not fused to Vgl-2. P-2 and P-3 ventrally each with a distinct ventral extension, P-4 stocky, ventral setae not exceeding the length of the segment, P-4 sword seta slightly proximal to posteroventral hair (Fig. 5B). I-L-5 setae S-1 and S-2 separated, S-1 curved, with concave adaxial margin, apically truncated and with a fine distomedial extension, 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 (Fig. 5C).

Female -Unknown.
Etymology -The new species is named after the province where the type locality is located.
Discussion -The new species from South Iran closely resembles Atractides gibberipalpis Piersig, 1898, a rhitrobiontic species from the Palaearctic. The specimens from Yazd province (central Iran), here assigned to the new species, were originally assigned by Pešić et al. (2004b) to A. gibberipalpis. Re-examination of this material reveals a diagnostic differences in the shape of genital field and S-1 (A. gibberipalpis: Ac larger, Ac-3 elongated, drop-shaped, anterior margin more or less indented; S-1 distally narrowed with bluntly pointed tip, see Gerecke 2003).
Atractides yunusi Pešić & Smit, 2021, a species recently described species from Kyrgyzstan (Pešić and Smit 2021a) resembles the new species in Ac arrangement and in a I-L with enlarged penultimate segment bearing a truncated sword seta S-1 but differs in shape of the genital field (anterior margin slightly convex, Ac-3 more roundish and smaller in size) and P-4 sword seta nearer to distoventral seta (Pešić and Smit 2021a).
Distribution -Iran; known from a high-order stream.