Fauna of free-living nematodes (Nematoda) of the waterbodies and watercourses of northern Irkutsk oblast, Russia

Abstract

The species diversity of free-living nematodes has been studied in the fresh waterbodies and watercourses of the Lena River basin, northern Irkutsk oblast: in the Chuya, Mama, Yuhtinka, and Vitim rivers; in Lake Teterinskoe and Lake Krasnoyarskoe; and in an unnamed lake near the settlement of Mama. Twenty-eight species belonging to 16 families and 9 orders are registered, and 6 species of these 28 are identified at the genus level only. Twenty-two species have been identified with certainty; 11 of them are eurybiont, 2 species are characterized by Holarctic distribution, 5 species are found in Eurasia, 1 species is found in Eastern Siberia, and 3 species are found at one site each. The species composition of the studied waterbodies and watercourses is usual and is presented mostly by the widespread nematode species. The most interesting findings include Tripyla dybowskii Tsalolikhin, 1976, which was previously considered a subendemic species of Lake Baikal. Three species are common to the fauna of Lake Baikal (two of them inhabit the splash zone). An illustrated description of the female of the rare species Aporcelaimellus samarcandicus (Tulaganov, 1949) is given.