Bathynella bazikalovae sp. n. and Bathynella rara sp. n. (Crustacea, Syncarida, Bathynellidae) from Lake Baikal

Illustrated descriptions of two species of the genus Bathynella Vejdovsky, 1882 are presented: B. bazikalovae Alekseeva, Krivorotkin et Timoshkin sp. n. and B. rara Alekseeva, Krivorotkin et Timoshkin sp. n. Both species are endemic to Lake Baikal. The first species was found in large numbers in the coastal zone of Bolshiye Koty Bay: in the splash zone, as well as in the depth range from the water’s edge to 0.5 m in a sandy substrate. The second species was found on the underwater Akademichesky Ridge at a depth of 350 m, in oxidized silt with dead Cladocera (their carapaces and ephippiums) and diatoms. The morphology of the new species was studied in detail using both scanning electron and light microscopy. An extensive comparison of the new species between themselves and with B. baicalensis Bazikalova, 1954 is given. The species differ in the armament of thoracopods 1–7, the structure of thoracopod 8 of females and males, the armament of the uropods and pleopods, and other morphological features. These discoveries confirm earlier assumptions concerning the much greater species richness of the Bathynellacea fauna of Lake Baikal.