Data on the structure and variability of the nucleotide sequence of the mtDNA cytochrome b gene of the northern pike Esox lucius L. from the rivers of the Kolyma, Volga, Don basins and the Anadyr River were obtained. Unique haplotypes were found, indicating limited gene flow between the studied populations. Northern pikes from the Volga and the Anadyr have a high level of genetic diversity. Low genetic diversity was noted in some populations of the Kolyma and Don basins. Phylogenetic analysis of the nucleotide sequences of the cytochrome b gene showed the presence of three genetic strains, A, B, and C, having a common root of origin. The high level of differentiation of the identified strains is apparently caused by the long-term reproductive isolation of the northern pike in several refugia, which were the source for the circumpolar distribution of this species.

According to the latest revision of the genus Microsomacanthus Lopez-Neyra, 1942 (Cestoda: Hymenolepididae), most parasites of ducks and gulls are assigned to two subgenera that differ morphologically and biologically: the nominative taxon M. (Microsomacanthus) and the new taxon M. (Leuckartсohnacanthus) Galkin, Regel, 2010. Species that have no place in these taxa remain, however, within the genus Microsomacanthus s. l. Molecular-genetic analysis of 9 Microsomacanthus species showed the presence in NJ-phylogenetic tree of nucleotide sequences of a fragment of the 18S rRNA gene of two clades. One of them is formed by 3 species of the subgenus M. (Microsomacanthus), another one – by 5 ones of M. (Leuckartсohnacanthus). Haplotype from Microsomacanthus s. l. arcuata differs significantly from representatives of both haplogroups. This confirms the existence of at least two subgeneric taxa within the genus Microsomacanthus, as well as the presence of species worthy of their own subgenus.

Nucleotide sequence polymorphism and haplotypic diversity of the cytochrome b gene were studied in samples of the Laxmann’s Shrew subspecies-Sorex caecutiens koreni from the populations of the Kolyma River basin and Chukotka Peninsula. Fifty-six cytb haplotypes differing among themselves by 87 mutations in 84 sites were found. The cytb haplotypes of individuals of the subspecies S. c. koreni and S. c. macropygmaeus were shown to belong to the same maternal mtDNA lineage; their monophyletic origin from the same ancestral haplotype Scb1 and the presence of identical cytb haplotypes in both subspecies were revealed. The mutual isolation of the shrew populations in the upper basin of the Kolyma River and Chukotka is shown. The proportion of intrapopulation genetic variability is 95.74

A significant polymorphism of the complete amino acid sequence of the cytb polypeptide was found in A. oeconomus of Northeast Russia and Alaska. 29 cytb isoforms were found in representatives of the Central Asian phylogroup, and 15 ones – in the Bering phylogroup, differing in 30 amino acid substitutions. The amino acid substitution F333L pretends to be a genetic marker of the Bering phylogroup. The methods of Snit, Bachinsky, Grantsem and TreeSAAP analysis reliably confirm the conservative type of amino acid substitutions, which indicates the effect of stabilizing selection on the cytb enzyme in tundra voles. Convergence of the amino acid sequence of the cytb polypeptide during divergence of the cytb nucleotide sequence – isoform FEcbCA-1 encodes 21 and FEcbBr-1-26 cytb haplotypes with high values of molecular diversity indices is revealed. This indicates a significant polymorphism in the nucleotide sequences of cytb haplotypes encoding the same amino acid sequence of the polypeptide. The rapid change of generations in this species causes the emergence of many mutations. Degeneracy of the genetic code ensures that populations of different genotypes encoding the same vital phenotypes are fixed in the gene pool. Apparently, the most common isoforms of FEcbCA-1 and FEcbBr-1 in the tundra voles’ populations are functionally optimal for the species in the ecological conditions of Northeast Russia and Alaska.

A fragment of 875 bp of the 18S rRNA gene was studied in 12 samples of Mesocestoides tetrathyridia from small mammals of 7 species collected in geographically distant localities. Five haplotypes were identified, differing from each other by 27 nucleotide substitutions in 24 sites. It has been found that the 18S rRNA haplotypes belong to two genetically distinct haplogroups. Molecular diversity indices were calculated for each of them. The conducted analysis allowed to suggest the following: 1) Mesocestoides sp. haplogroups A and B belong to two different species, but do not belong to any of the confirmed species of the genus; 2) the deletion of bp 729–747 and the insertion at site 761 of guanine can be regarded as a genetic marker for the species Mesocestoides litteratus.

A fragment of 875 bp of the 18S rRNA gene was studied in 12 samples of Mesocestoides tetrathyridia from small mammals of 7 species collected in geographically distant localities. Five haplotypes were identified, differing from each other by 27 nucleotide substitutions in 24 sites. It has been found that the 18S rRNA haplotypes belong to two genetically distinct haplogroups. Molecular diversity indices were calculated for each of them. The conducted analysis allowed to suggest the following: 1) Mesocestoides sp. haplogroups A and B belong to two different species, but do not belong to any of the confirmed species of the genus; 2) the deletion of bp 729–747 and the insertion at site 761 of guanine can be regarded as a genetic marker for the species Mesocestoides litteratus.

Data on the nucleotide sequence variability of the mtDNA cytochrome b gene of the European perch ( Perca fluviatilis Linnaeus, 1758) from the rivers of the Volga and the Kolyma basins were obtained. An assessment of the genetic diversity of the European perch from the studied populations was carried out. A high level of divergence was noted between the perch samples from the rivers of different regions. At the same time, it was shown that, according to the genetic parameters, the samples of the European perch from the rivers of the same water basin had statistically significant differences. Phylogenetic analysis based on the found haplotypes of the mtDNA cytochrome b gene led to the conclusion that the Kolyma perch cannot claim the status of a subspecies of P. fluviatilis .

The article presents the data on structures of the nucleotide sequence fragments of the 12S ribosomal RNA gene (12S rRNA) for 19 tetrathyridia specimens of the genus Mesocestoides Vaillant, 1863 from representatives of 10 insectivore and rodent species from different regions of RussiaТs East and Alaska (USA). For the first time, the participation of three shrew species in the life cycle of Mesocestoides has been established. Nucleotide sequence fragments of the 12S rRNA gene have been analyzed phylogenetically. The researched tetrathyridia do not assumingly belong to any of the confirmed species of the genus; however, the identity of five of the 12S rRNA sequence fragments from micromammalian tetrathyridia and two nucleotide sequences of 12S rRNA from carnivorous mammals of Mongolia, placed in GenBank, has been established.

The nucleotide sequence polymorphism and haplotype diversity of the cytochrome b gene in samples of the tundra vole (Alexandromys oeconomus) from Northeast Asia and Alaska were studied. Sixty-three haplotypes of the cytb gene (51 variants of Central Asian and 12 of Beringian genetic lineages), differing among themselves by 94 mutations, were found. The Upper Kolyma River is inhabited by voles of the Central Asian clade. A mixed population of this species in the basin of the Omolon River (right tributary of the Kolyma River) was found. In Chukotka and Alaska, only specimens of the Beringian phylogroup were found. The genetic differences between all samples are statistically significant. Genetic data of A. oeconomus populations of the Kolyma River basin, Alaska, and Northern Okhotomorye (Northern Sea of Okhotsk area) were compared. A total of 231 substitutions at 226 sites were found in the nucleotide sequence of the mtDNA cytochrome b gene in voles from both clades. The values of molecular diversity indices testify to the stability of populations with a high value of effective abundance over a long period of time. An analysis of the population gene pool formation was performed and a reconstruction of the complex dispersal history of this species across Northeast Asia was proposed.

The nucleotide sequences of the mtDNA cytb and COI genes of the chum salmon Oncorhynchus keta (Walbaum) from the rivers of the Sea of Okhotsk northern coast (Yama - donor, Kulkuty - artificially created population) have been determined. Polymorphism of the studied molecular markers has been noted. Unique haplotypes occurring only in one of the studied populations were found. The genetic distance calculated between the Yama and Kulkuty chum salmon populations indicates the absence of statistically significant differences between them. Nevertheless, the genetic diversity in a sample from an artificially created population tends to increase comparing to indicators characterizing the donor population. This may be associated with the formation peculiarities of the Kulkuty chum salmon genetic structure. Besides, the influence of the straying, amounted to 4 %, cannot be excluded. Apparently, haplotypes introduced as a result of inter-population exchange are successfully maintained through artificial reproduction. This has caused some change in the gene pool of the artificial population compared to the donor one.

Data on the variability of the nucleotide sequence of the mtDNA cytochrome b gene and the amino acid sequence of the polypeptide encoded by it were obtained in the Siberian sucker Catostomus catostomus rostratus (Tilesius, 1814) from Lake Darpir (basin of the Kolyma River, northeast of Siberia) for the first time. Signals of molecular adaptation in the Siberian sucker from the water bodies of the Kolyma-Indigirka Lowland were found in small numbers and only in the sample from Lake Darpir. This is probably defined by the high conservatism of the amino acid sequence of mitochondrial proteins. At the same time, it is not inconceivable that adaptive variants of the cytochrome b protein were lost by representatives of this species during climate change in the Holocene. It is noted that long-term reproductive isolation of the Siberian sucker, a subspecies of the common sucker from North America, has led to significant intraspecific divergence. Despite the divergence of the haplotypes encoding the Fch1 variant of the cytochrome b polypeptide, this form of the enzyme is widespread throughout the entire range of the species and is probably the most functionally effective.

Based on our own data and that borrowed from available sources, polymorphism of the cytochrome b polypeptide of the gray red-backed vole (Craseomys rufocanus Sundevall, 1846) is considered in the populations of Northeast Asia. Twenty-seven isoforms of the enzyme amino acid sequence were found. A comparative analysis of the frequencies of the cytochrome b variants was carried out in the samples of the gray red-backed vole. The localization of amino acid substitutions was determined in the model of the secondary structure of the enzyme. The method of TreeSAAP analysis, and Snit’s, Bachinsky’s, and Grantsem’s methods reliably confirm the conservative type of amino acid substitutions, which indicates the effect of stabilizing selection aimed at the preservation of two physicochemical properties in a number of polypeptide variants.

— Data on the variability of the mtDNA nucleotide sequence of cytochrome b of pink salmon from successive generations were obtained. There was a higher level of divergence between samples of the line of even years from rivers in different regions than in the successive generation. At the same time, some geographically close populations had statistically significant differences in the genetic parameters. The calculated proportion of intergroup genetic dispersion indicated that the divergence of successive generations of pink salmon occurred in the relatively recent historical past. An analysis of the genetic variability of pink salmon showed that the level of differentiation in populations of the northern Sea of Okhotsk from different fishing grounds was lower than the level observed between the localities within each area. We detected amino acid substitutions in the primary structure of the Cytb protein of pink salmon, indicating the effect of positive stabilizing selection.

казано, что обыкновенная щука из рек колымоиндигирского бассейна и р.Анадырь имеет существенные морфологические отличия (череш

ВВедениекрасная полевка (clethrionomys rutilus Pallas, 1779) -голарктический вид, ареал которого занимает обширные, преимущественно северные территории евразии и Северной Америки

Средняя бурозубка (Sorex caecutiens Laxmann