No 2 (2020)

A comparative analysis of distinctive morphological features of sagittae in the Thymallus species from Lake Baikal and the Barguzin River has been done. The otolith shape was described using values of radii and the Fourier descriptors. It is demonstrated that the otoliths of Thymallus species have a similar structure. The otolith outline analysis allowed to differentiate the samplings according to the morphotypes that characterize them. No significant differences in length, width, perimeter and area of the otoliths in the Thymallus species have been identified. However, some differences in the shape of otoliths were described in T. baicalolenensis; they had a less developed pararostrum and more salient ventral edge than the otoliths of T. baicalensis from the lakes Balan-Tamur and Baikal. The otolith shape analysis can be widely applied for basic research of microevolutionary processes, delimitation of natural populations and preservation of genetic diversity as well as for defining the structure of the commercial stock.

Currently, with an increase in technological progress, anthropogenic impact on the environment is increasingly apparent. Since surface waters are the most vulnerable part of the natural environment, a detailed study of water pollution is one of the urgent tasks. This article presents the results of the instrumental measurements and the assessment of the pollution of the surface waters in the littoral zone of the Barguzin and Chivyrkuy bays of Lake Baikal. To determine the degree of water pollution, we compared hydrochemical indicators with the standards of the maximum permissible concentrations. We revealed that in different parts of the Chivyrkuy Bay, water quality varies in a wide range from slightly polluted to very polluted and, in some cases, highly polluted. The waters in the Barguzin Bay can mainly be classified as slightly polluted, and only in some areas – as moderately polluted or highly polluted. According to the comprehensive water pollution index, the waters in the Chivyrkuy and Barguzin bays is assessed as conditionally polluted and conditionally pure, respectively.

A nuclear marker, an intron of ATP synthase α-subunit gene, used to determine phylogenetic relationships between 22 species of the family Baicaliidae (Caenogastropoda: Rissooidea) indicated two genetic groups of these gastropods in Lake Baikal. The obtained groups partially coincide with the clusters revealed by the mitochondrial COI gene and do not fully coincide with the modern taxonomy of the family. Thirteen species of the first group inhabit different sediments (silty sand, sand, stones, and rocks), eight out of the nine species from the second group are psammobionts. Both genetic groups include eurybathic and stenobathic species widely distributed in the North, Middle and Southern Basins of the lake, as well as species, whose habitats are limited to one or two basins. Phylogenetic analysis suggests that the main way of baicaliids speciation was the repeated occupation of the same habitats by different ancestral forms. Sculpture of the shells (ribs, carina and/or periostracal hairs/plates) also most likely appeared independently in each group due to similar adaptation.