Recent results of molecularphylogenetic studies of endemic invertebrates inhabiting Lake Baikal

Lake Baikal and its invertebrates became a subject of systematic evolutionary studies more than a century ago. Exceptional taxonomic diversity of the lake’s fauna, high variability of habitats and large volume of auxiliary knowledge on the ecosystem enables one to study fine details of speciation mechanisms hardly accessible in other model systems. Parallel to the development of technological and methodological potential of biology most of new approaches were employed in studies of Lake Baikal. This review deals mostly with the results obtained during last two decades by means of molecular phylogenetics. The main common features found to date include, first of all, a relatively young age of the most recent common ancestor of the majority of species flocks. Second, it was found that almost all speciation events studied took place in sympatry and according to quite complicated scenarios. The latter is due to the fact that in the course of geological evolution of Lake Baikal there were no or very few episodes of its fragmentation sufficiently long for allopatric mechanisms to leave detectable traces. Reproductive barriers may temporarily disappear causing frequent mitochondrial or nuclear introgressions. As a result, intermediary forms of organisms of unclear taxonomic identity are a common occurrence. Another interesting feature is a practically absolute absence of evidence for co-evolution even of ecologically tightly connected organisms

DNA metabarcoding of benthic algae and associated eukaryotes from Lake Baikal in the face of rapid environmental changes

Here we report new data describing the biodiversity of phytobenthic communities based on DNA-metabarcoding using the 18S rDNA marker and the Illumina MiSeq system. The study was initiated due to the blooming of filamentous algae (mainly of the genus Spirogyra) and cyanobacteria in the coastal zone of Lake Baikal under climate change and anthropogenic impact. The composition and taxonomic diversity of algae and other organisms associated with them on different sites of Lake Baikal (near Bolshoi Ushkaniy Island, in Listvennichny Bay) and in the Kaya (within the city of Irkutsk, located in the same drainage basin as Lake Baikal) were determined using DNAmetabarcoding. About 15 thousand reads of the 18S rRNA marker were obtained by applying NGS (next-generation sequencing). The species of algae dominating in the number of reads, as well as the difficult-to-identify taxa (Stramenopiles, Alveolata, Euglenozoa, Chromista, Rhizaria, Amoebozoa, etc.), which play an important role in the functioning and formation of the structure of algal communities, were revealed. The Shannon index of the communities studied ranges from 1.56 to 2.72. The advantages and weaknesses of using DNA-metabarcoding based on the 18S rRNA gene fragment for studying the structure of algal communities are shown. The advantage of this method is the possibility to more fully determine the diversity of eukaryotes taxa, which are difficult to identify by morphology, without involving a large number of specialists, while the disadvantage of the method is the distortion that may occur during the PCR. Here, ways of solving this problem are proposed. The results of the study show that the analysis of the minor component of the eukaryotic community in samples (organisms with low biomass) consisting of a mixture of multicellular and unicellular organisms requires a read-depths of at least 100,000 sequences per sample. In general, the DNA-metabarcoding method is recommended for studying the structure of algal communities and eukaryotes associated with them

Clinical features of post-COVID-19 period. Results of the international register “Dynamic analysis of comorbidities in SARS-CoV-2 survivors (AKTIV SARS-CoV-2)”. Data from 6-month follow-up

Aim. To study the clinical course specifics of coronavirus disease 2019 (COVID-19) and comorbid conditions in COVID-19 survivors 3, 6, 12 months after recovery in the Eurasian region according to the AKTIV register. Material and methods.The AKTIV register was created at the initiative of the Eurasian Association of Therapists. The AKTIV register is divided into 2 parts: AKTIV 1 and AKTIV 2. The AKTIV 1 register currently includes 6300 patients, while in AKTIV 2 — 2770. Patients diagnosed with COVID-19 receiving in- and outpatient treatment have been anonymously included on the registry. The following 7 countries participated in the register: Russian Federation, Republic of Armenia, Republic of Belarus, Republic of Kazakhstan, Kyrgyz Republic, Republic of Moldova, Republic of Uzbekistan. This closed multicenter register with two nonoverlapping branches (in- and outpatient branch) provides 6 visits: 3 in-person visits during the acute period and 3 telephone calls after 3, 6, 12 months. Subject recruitment lasted from June 29, 2020 to October 29, 2020. Register will end on October 29, 2022. A total of 9 fragmentary analyzes of the registry data are planned. This fragment of the study presents the results of the post-hospitalization period in COVID-19 survivors after 3 and 6 months. Results. According to the AKTIV register, patients after COVID-19 are characterized by long-term persistent symptoms and frequent seeking for unscheduled medical care, including rehospitalizations. The most common causes of unplanned medical care are uncontrolled hypertension (HTN) and chronic coronary artery disease (CAD) and/or decompensated type 2 diabetes (T2D). During 3- and 6-month follow-up after hospitalization, 5,6% and 6,4% of patients were diagnosed with other diseases, which were more often presented by HTN, T2D, and CAD. The mortality rate of patients in the post-hospitalization period was 1,9% in the first 3 months and 0,2% for 4-6 months. The highest mortality rate was observed in the first 3 months in the group of patients with class II-IV heart failure, as well as in patients with cardiovascular diseases and cancer. In the pattern of death causes in the post-hospitalization period, following cardiovascular causes prevailed (31,8%): acute coronary syndrome, stroke, acute heart failure. Conclusion. According to the AKTIV register, the health status of patients after COVID-19 in a serious challenge for healthcare system, which requires planning adequate health system capacity to provide care to patients with COVID-19 in both acute and post-hospitalization period

The complete mitochondrial genomes of four Baikal molluscs from the endemic family Baicaliidae (Caenogastropoda: Truncatelloida)

AbstractHere, we present the complete mitochondrial (mt) genomes of four members of the Baicaliidae Fisher, 1885, a truncatelloidean family that is endemic to Lake Baikal (East Siberia). The mt genomes are those of Korotnewia korotnevi (15,171 bp), Godlewskia godlewskii (15,224 bp), Baicalia turriformis (15,127) and Maackia herderiana (15,154 bp). All these mt genomes contain 13 protein-coding genes, 2 ribosomal RNA (rRNA) genes and 22 transfer RNA (tRNA) genes. We detected non-canonical base pairs in some of the tRNA genes and variable numbers of non-coding spacers; some tRNAs do not have a TψC loop. We found gene order to be highly conserved in these Lake Baikal species and similar to the majority of caenogastropod mt genomes available on GenBank. A position of the putative control region is delimited to the non-coding region between trnF and the cox3 gene. It contains the ‘GAA(A)nT’ motif at the 3′ end and is similar to the replication origin found in most Caenogastropoda studied to date. We also compared the evolutionary rates of different genes to evaluate their use in different kinds of population or phylogenetic studies of this group of gastropods.</jats:p

Comparative and evolutionary genomics and proteomics 203 POPULATION GENETIC POLYMORPHISM OF ENDEMIC MOLLUSCS BAICALIA CARINATA (MOLLUSCA: CAENOGASTROPODA)

SUMMARY Motivation: Sets of aligned nucleotide sequences resulting population level genetic polymorphism studies are generally believed to contain more ecologically and evolutionary meaningful information than is uncovered by phylogenetic analysis. This paper aims at the elucidation of population structure of Baikalian endemic snail Baicalia carinata. Results: Basing on 97 nucleotide sequences of the 588 base pairs long fragment of mitochondrial gene coding for 1 subunit of cytochrome с oxydase of Baikalian endemic gastropod Baicalia carinata (Dybowski, 1875) we show that this species is split into three clades, which correspond to three populations: Southern, North-Western and NorthEastern. We used the Mann and Whitney rank criterion in order to estimate the statistic significance of genetic differences between the populations