No 2 (2018)

In recent years, mitochondrial DNA (mtDNA) has been used to solve many phylogenetic problems at different taxonomic levels. Previously, the nucleotide sequences of the mitochondrial genomes of the Baikal endemic sponge species of the Lubomirskiidae family have been identified. Their phylogenetic links are still being actively studied, and their systematics is considered to be not definitive. In order to study the mechanisms of speciation and evolution of mtDNA, special attention is paid to the investigations of noncoding DNA. We have studied the characteristics of the organization of the intergenic mtDNA regions in the Baikal sponges on the example of the longest region between the tRNATyr and tRNAIle genes of the species L. baicalensis, S. papyracea, R. echinata, and B. intermedia profundalis. A comparative analysis of the sequences has shown the presence of secondary structures represented by individual hairpins and complex multilevel structures. Based on a comparative analysis of secondary structures, we have suggested their role as both regulative elements and potential mobile elements. We have determined the continuity of these structures among representatives of different genera of the Lubomirskiidae family. The highest similarity in their distribution and localization was found in phylogenetically related species of the Baikal sponges.

We have studied the fauna of Hydra in the waters of the Baikal region using morphological and molecular genetic methods. By the external morphological features of the structure of the polyp and the microscopic study of nematocysts, we have identified four species belonging to three different genetic groups: “oligactis group” (Hydra oligactis, H. oxycnida), “braueri group” (H. circumcincta) and “vulgaris group” (H. vulgaris). Molecular phylogenetic analysis has confirmed the species status of the hydras studied. The intraspecific genetic distances between the Baikal and European hydras are 1.5–4.2% and 0.4–2.7% of the substitutions in COI and ITS1–5.8S–ITS2 markers, respectively, while, interspecific distances for different species significantly exceed intraspecific and amount to 9.8−16.1% and 6.4−32.1% of substitutions for the markers COI and ITS1–5.8S–ITS2, respectively. The temperature regime of the water and the availability of food resources, which play a key role in the reproduction of hydras, determine the habitats of the identified species. The research performed has replenished the regional fauna with species whose findings were previously considered presumptive or doubtful. The first record of H. vulgaris in the artificial reservoir near the Angara River (Lake Kuzmikhinskoye) will help to clarify the distribution of this species.

In recent years, a large scale ecological crisis has been observed in the Lake Baikal ecosystem. It is clearly shown by several signs, including the mass disease of sponges in the coastal zone. To investigate the causes of the crisis, the composition of symbiotic communities in sponges was investigated in 2015 by sequencing of the 16S rRNA gene in three locations of the lake. The methods of fractal theory were adopted in order to detect a fractal structure in the distribution of the sequencing reads, being considered as fragments of the 16S rRNA gene for individual bacteria within the collected samples. The fractal-like distributions were constructed for the seven most abundant phylotypes, and the observed properties of the distributions reflect microevolution processes within the selected genera and species. The values of the fractal dimension, evaluated for the distributions, are observed to correlate with an anthropogenic load at the place of sample collection, for the Flavobacterium and Synechococcus genera. The sampling sites were also observed to be associated with the properties of the distributions for chloroplasts of Trebouxiophyceae algae, the endosymbiont of Lubomirskia baicalensis sponge.The long-scale time dependency of fractal dimension was also evaluated for the data from temperature detectors in four locations of Lake Baikal. The values of the fractal dimension for fluctuations of temperature are also observed to be associated with an anthropogenic load in the place of measurement. The consistency of both approaches validates the usefulness of fractal-based methods in the interpretation of the experiments designed to study the ecological crisis in Lake Baikal.

At present, the littoral zone of the Southern Baikal is under anthropogenic impact. The negative changes in underwater vegetation landscapes most dramatically appeared near the Listvyanka settlement. In this study, we compare phytoplankton assemblages from the surface layer (ca. 1.5 m depth) near the Listvyanka settlement collected during 1990-1995 and 2016-2018. We have compared phytoplankton data with solar irradiance and air temperatures. Phytoplankton community was represented by 70 taxa, where Bacillariophyta and Cryptophyta dominated the biomass. In 2016-2018, there were no significant differences in biomass or abnormal seasonal vegetation of the studied phytoplankton taxa compared to 1990-1995