A review of the chironomid fauna (Diptera: Chironomidae) in the Middle Volga basin within the Republic of Tatarstan, Russia

Abstract. Data on the fauna of chironomids in water bodies of various types in the Middle Volga region within the Republic of Tatarstan (Russia) are summurized. Studies of the chironomid fauna were carried out as part of monitoring observations of the state of water bodies in the Republic of Tatarstan. Permanent observations were carried out on Kazanka, Vyatka, Zay and Stepnoy Zay rivers, as well as on the Kuybyshev Reservoir and Sredniy Kaban and Raifskoe lakes. Studies were carried out on some small rivers in the east of Tatarstan (Pre-Kama and Trans-Kama regions). In total, 199 species of chironomids from five subfamilies were registered: Tanypodinae (33 species), Diamesinae (8 species), Prodiamesinae (5 species), Orthocladiinae (53  species), Chironominae (100  species). Among recorded species, 74  ones have a Holarctic distribution, 55 species are Palaearctic and three species are distributed outside the Holarctic. The highest species diversity of chironomids was recorded for the Kuybyshev Reservoir and the Stepnoy Zay River. The specificity of the chironomid fauna of the studied water bodies can be explained by their geographical features and hydrochemical regime. The appearance of species new to the fauna of the region, originally inhabiting the northern and eastern regions of Russia, was registered, that indicates their settlement to more southern regions.