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Arctic regions of northeastern Asia represent areas of secondary contact of the glacial phylogenetic lineages of charrs belonging to the genus Salvelinus (Salmoniformes: Salmonidae). However, the post‐glacial dispersion of charr across Arctic regions is poorly understood, as knowledge of populations from Chukotka and its neighbouring areas remains limited. Specifically, there is no clear understanding of which charr species inhabit significant regions of Chukotka from the sea coasts to the Kolyma drainage. In this study, we explored the affiliation of lacustrine charrs from the Chukotka area with (1) the Arctic lineage of Taranetz' charr (Salvelinus taranetzi); (2) the Bering lineage of Northern Dolly Varden (Salvelinus malma malma) and (3) the Siberia and Atlantic lineages of Arctic charr (Salvelinus alpinus). We analysed sequence variation of the mitochondrial DNA control region (mtDNA CR; 960 base pairs) and genotyped seven microsatellite loci of nuclear DNA from charr collected at 13 sampling sites. We found different consequences of secondary contact: (1) complete fixation of introgressed mtDNA (mitochondrial capture) and (2) preservation of several mtDNA lineages with the absence of contemporary gene flow between resident populations. Combining the distribution patterns, phylogenetic network topology and knowledge of the glaciation history of the region, we propose two zones of secondary contact of the glacial lineages in Chukotka–Kolima‐Chukotka River system and Paleo‐Amguema River–from where charrs with introgressed genomes spread throughout this range. However, in some cases, the process of foreign mtDNA capture likely occurs in a more localised manner. [ABSTRACT FROM AUTHOR]

The Pacific smelt Osmerus dentex is widely distributed in the North Pacific and Arctic seas and belongs to the species that may shed light on the biogeography and evolutionary history of Arctic marine fauna. O. dentex came into existence in the northwestern Pacific at the Pliocene-Pleistocene border and could widely spread along the Eurasian and North American coasts. We assessed the impact of global climatic and geological changes on the formation of the genetic structure of O. dentex in the Eurasian parts of the species area using a variety of phylogenetic methods and molecular dating. The results were interpreted in conjunction with paleoclimatic evidence. Phylogeographic patterns based on cytb and coI sequences, and RFLP ND3/ND4L/ND4 and A8/A6/COIII/ND3 mtDNA regions for 462 Pacific smelts from 25 Eurasian locations were analyzed. Our results suggest that (1) geographical distribution observed for mtDNA haplotypes resulted from influences of historical range expansions, episodes of long-distance colonization and restricted dispersal; (2) the main refugium was located in the northwestern Pacific and the genetic similarities observed among and within geographical regions probably originated from postglacial recolonization from common sources; (3) an additional small refugium in the White Sea existed in the Late Pleistocene. [ABSTRACT FROM AUTHOR]

The complete mitochondrial genomes were sequenced from three individuals of the endemic charr Salvelinus sp. 4 [ from Lake Nachikinskoe (Kamchatka, Russia). The complete mitochondrial genomes were 16,654 bp in size; the genome organization and GC content (45.6%) was consistent with charr mitochondrial genomes published previously. The low level of sequence divergence detected between the Salvelinus sp. 4 and the GenBank Salvelinus taranetzi genomes indicated recent divergence and their origin from a common ancestor. Our results could play an essential role in resolving the conflict over current taxonomic status of endemic charr in genus Salvelinus. [ABSTRACT FROM AUTHOR]

Milky hemolymph syndrome (MHS) caused by a bacilliform virus (BV) was found in tanner crab Chionoecetes bairdi in the shelf zone of Kamchatka. The prevalence of the disease varied from 0.18 to 1.02%. A total lesion of the cells of the interstitial connective tissue and the connective tissue component of all internal organs was noted, which was expressed in the hypertrophy of their nuclei. In addition, hypertrophy of fixed phagocytes and circulating hemocytes was noted. Ultrastructural analysis of the tissues confirmed that in the interstitial connective tissue of pathologically altered organs, virus particles of two morphotypes were found - rod-shaped and globular. In the cytoplasm of infected cells, bands of microtubules formed near where viral particles were concentrated. In the area of contacts at the poles of microtubules, successive stages of the transformation of rod-shaped viruses into globular viruses was observed. The bacilliform virus that infects C. bairdi is structurally very similar to CoBV found in Chionoecetes opilio. Structural features are characteristic of representatives of fam. Nimaviridae. The molecular data obtained suggest that the virus causing MHS in C. bairdi is systematically very close, if not identical, to CoBV., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

A parasitic dinoflagellate of the genus Hematodinium was found off the Pacific coast of Kamchatka in three species of crabs: red king crab Paralithodes camtschaticus, tanner crab Chionoecetes bairdi, and spiny king crab Paralithodes brevipes. This is the first detection of Hematodinium in spiny king crab. The results of the genetic analysis showed that the pathogen found in P. brevipes, P. camtschaticus, and C bairdi from the Avacha and Kronotsky bays off the Pacific coast of Kamchatka was the same or very close to the Hematodinium sp., which infects many species of crustaceans in the Northern Hemisphere. The prevalence of infection was 0.2% for tanner crabs and 2.7% for red king crabs. Due to a limited sample size, we were unable to calculate the prevalence for spiny king crabs and female red king crabs. Both the macroscopic and microscopic signs of the pathology were similar in all diseased crabs. The differences in the micromorphology of the Hematodinium cells we found in the three crab species, including the presence or absence of trichocysts, the shape of the plasmodia, and the structure of pore complexes, are most likely related to the life cycle and the physiology of the parasite. The results of the genetic analysis showed that the pathogen found in P. brevipes, P. camtschaticus, and C. bairdi from the Avacha and Kronotsky bays of the Pacific coast of Kamchatka was the same or very close to the Hematodinium sp., which infects many species of crustaceans in the Northern Hemisphere., (Copyright © 2021 Elsevier Inc. All rights reserved.)

An infection caused by a rickettsia-like organism (RLO) was detected in the blue king crab Paralithodes platypus from the eastern Sea of Okhotsk. The external signs of the disease are lethargy and an empty gastrointestinal tract. Dissection of infected individuals revealed that their hepatopancreas was light yellow in color. The causative agent of infection is Gram-negative rod-shaped bacterium targeted exclusively at hepatopancreas tissues. In the cytoplasm of infected cells, the bacteria are enclosed in parasite vacuoles or located immediately in cytosol. An ultrastructural analysis showed two main morphological types corresponding to the life cycle stages in the RLO: the vegetative stage of intermediate bodies, characterized by growth and division processes, and the infection stage of elementary bodies, which are spore-like non-dividing short rods surrounded by a multilayered membrane and having an osmiophilic inclusion body. At the terminal stage of infection, as a result of lysis of the infected cells, the RLO enters the lumen of the hepatopancreatic tubules which contributes to the spread of infection. According to genetic analysis based on 16S rRNA gene sequences, the RLO from P. platypus is most closely related to the Candidatus Hepatobacter penaei, NCBI #JX981946 (94.7% similarity) and NCBI #KY363553 (94.1% similarity). The high level of genetic differences (more than 5%) of the studied pathogen, along with the structural features, allows characterizing the RLO isolated from P. platypus as a new species of the genus Candidatus Hepatobacter paralithodi nov. sp., NCBI #MK928971., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Comparison of coding nucleotide sequences of the paralogous GH1 and GH2 genes, as well as of the growth hormone amino acid sequences, in the species of closely related salmonid genera Salvelinus, Oncorhynchus, and Salmo was performed. It was demonstrated that, in different groups of salmonids, the amino acid substitution rates were considerably different. In some cases, an obvious discrepancy between the divergence of growth hormone genes and phylogenetic schemes based on other methods and approaches was revealed. These findings suggest that the reason may be multidirectional selection at duplicated genes at different stages of evolution.