R.M. Kamaltynov

Population Structure of the Baikalian Amphipod Gmelinoides fasciatus (Stebbing)

Using the data on 71 individual sequences of the gene for the mitochondrial cytochrome-c-oxidase subunit one, molecular and phylogenetic characterization of the Baikalian amphipod, Gmelinoides fasciatus (Crustacea, Amphipoda), was performed. Interspecific polymorphism was demonstrated. Four main amphipod populations, Southeastern, Southwestern, Northern, and Central, were distinguished. A low level of genetic diversity typical of Southwestern population was revealed. For its explanation, the bottleneck hypothesis was proposed.

Evolution of mitochondrial genomes in Baikalian amphipods

BackgroundAmphipods (Crustacea) of Lake Baikal are a very numerous and diverse group of invertebrates generally believed to have originated by adaptive radiation. The evolutionary history and phylogenetic relationships in Baikalian amphipods still remain poorly understood. Sequencing of mitochondrial genomes is a relatively feasible way for obtaining a set of gene sequences suitable for robust phylogenetic inferences. The architecture of mitochondrial genomes also may provide additional information on the mechanisms of evolution of amphipods in Lake Baikal.ResultsThree complete and four nearly complete mitochondrial genomes of Baikalian amphipods were obtained by high-throughput sequencing using the Illumina platform. A phylogenetic inference based on the nucleotide sequences of all mitochondrial protein coding genes revealed the Baikalian species to be a monophyletic group relative to the nearest non-Baikalian species with a completely sequenced mitochondrial genome - Gammarus duebeni. The phylogeny of Baikalian amphipods also suggests that the shallow-water species Eulimnogammarus has likely evolved from a deep-water ancestor, however many other species have to be added to the analysis to test this hypothesis.The gene order in all mitochondrial genomes of studied Baikalian amphipods differs from the pancrustacean ground pattern. Mitochondrial genomes of four species possess 23 tRNA genes, and in three genomes the extra tRNA gene copies have likely undergone remolding. Widely varying lengths of putative control regions and other intergenic spacers are typical for the mitochondrial genomes of Baikalian amphipods.ConclusionsThe mitochondrial genomes of Baikalian amphipods display varying organization suggesting an intense rearrangement process during their evolution. Comparison of complete mitochondrial genomes is a potent approach for studying the amphipod evolution in Lake Baikal.

The complete mitochondrial genome of a deep-water Baikalian amphipoda Brachyuropus grewingkii (Dybowsky, 1874)

Abstract In this study, we present a complete mitochondrial genome of a deep-water amphipoda Brachyuropus grewingkii (Dybowsky, 1874) from Lake Baikal. A circular mitochondrial DNA has 17,118 bp in length and contains 13 protein-coding genes, two ribosomal RNA genes, 22 transfer RNA genes, a putative control region, and five intergenic spacers. An extended control region and altered positions of some tRNA genes distinguish mitochondrial genome of B. grewingkii from the mitochondrial genomes described for other Baikalian amphipoda species.

The complete mitochondrial genome of Baikalian amphipoda Eulimnogammarus vittatus Dybowsky, 1874

Abstract A complete mitochondrial genome sequence of amphipoda Eulimnogammarus vittatus Dybowsky, 1874 from Lake Baikal was obtained using next-generation sequencing approach. Mitochondrial DNA with the length of 15,534 bp contains 13 protein-coding genes, 2 ribosomal RNA, 23 transfer RNA and non-coding sequences: a putative control region and 7 intergenic spacers. A brief comparative analysis of mitochondrial genomes of E. vittatus and its sister species Eulimnogammarus verrucosus was performed.

THE CHROMOSOMES OF BAICALASELLUS ANGARENSIS (ISOPODA, ASELLIDAE)

To elucidate the cytotaxonomic relationships of endemic Baicalian asellides, the mitotic and meiotic chromosome configurations of Baicalasellus angarensis (Isopoda) were investigated. It was shown that the haploid chromosome number of B. angareresis is: n = 8; sex chromosomes have not been found. The karyotype of B. angarensis was found to be strikingly similar to the karyotype of Asellus aquaticus. It differs from the latter only by the morphology of a single chromosome pair and the number of chiasmata in metaphase 1. On the other hand, it differs markedly from the Japanese Asellus hilgendorfi. Possible implications of this finding on the current view of the origin of Baicalian isopods are discussed.

Genetic differentiation of gammarid (Eulimnogammarus cyaneus) populations in relation to past environmental changes in lake baikal

Publisher Summary The gammarid Eulimnogammarus cyaneus,endemic to Lake Baikal, occurs exclusively in the littoral zone of the stony or rocky shore of the lake. Individuals of the gammarid, Eulimnogammarus cyaneus in Lake Baikal are genetically differentiated into two major groups, largely corresponding to the bathymetric division of lake between the north and south-central basins. As there appears to be no extrinsic (physical) barrier to genetic mixing between them in the present state of the lake, the two groups are considered to be separated into different parts of the lake, and thereafter came to contact at a narrow marginal zone of their distribution, around the Olkhon Strait. The southern group is differentiated into further two groups at the Angara River outlet, which is perhaps caused by the formation of the Angara River as a reproductive barrier during the Late Pleistocene. The situation of populations on Olkhon Island is complicated. Two populations (24 and 25) on the southwest coast are closely related to the southern group, whereas those on other areas are akin to the northern group. It is likely that those populations came into secondary contact after the breakdown of the previously existed extrinsic barrier. In the contact zone, some special mechanism such as hybrid breakdown may be operating. However, this needs to be substantiated in future studies.