Shells of type specimens of Gyraulus takhteevi sp. n. and G. acronicus Férussac, 1807). A Holotype G. takhteevi sp. n. B–E Paratypes G. takhteevi sp .n. A–C morph 1 with narrow spire D, E morph 2 with wide spire F–G G. acronicus from Krestovka River: F young individual F mature individual after 5 months of a cultivation. Abbreviations: a – aperture view; b – right side with umbilicus, c – left side with spire. Scale bar 1 mm.