ABSTRACT
Baikal sculpins are the most species-rich and ecologically diverse group of fishes in the Lake. We analyzed complete mitochondrial genomes from four species of the endemic Baikal genus Batrachocottus (B. baicalensis, B. multiradiatus, B. talievi, and B. nikolski). Mitogenome sequences are 16,523-16,535 bp in length with a mitogenomic organization and gene arrangement identical to that of typical teleosts. Phylogenetic analysis using the Bayesian method positioned B. baicalensis outside the monophyletic clades of the genus Batrachocottus. Batrachocottus multiradiatus and B. talievi are sister species.
ABSTRACT
Coregonid fishes are among the most successful groups in the subarctic, boreal, and subalpine fresh waters of the northern hemisphere. Limnetic-benthic sympatric species-pairs from two different evolutionary lineages, the North American lake whitefish (Coregonus clupeaformis species complex), and the European whitefish (Coregonus lavaretus species complex), are becoming the subject of close attention to explore the role of natural selection during the ecological speciation. Baikal endemic coregonids, limnetic omul (Coregonus migratorius), and benthic lacustrine whitefish (Coregonus baicalensis) are the only representatives of another unique lineage that has not left the lake since the divergence from the two above. Due to Pleistocene oscillations sympatric limnetic-benthic divergence has been replicated here many times within the same water body over a long geological period in contrast to both Europe and America where sympatric species-pairs are the results of post-glacial secondary-contacts between glacial isolates during the Late Pleistocene on the territory of each continent. Mitochondrial genomes encode genes that are essential for respiration and metabolism. Data on complete mitogenomes of Baikal endemic coregonids provided here will complement ongoing investigations on energy metabolism as the main biological function involved in the divergence between limnetic and benthic whitefish.
ABSTRACT
Sculpins are predominantly benthic sit-and-wait predators that inhabit marine and freshwaters of the Northern Hemisphere. In striking contrast to riverine relatives, sculpins endemic to Lake Baikal have diversified in both form and function, with multiple taxa having adaptations for pelagic and bathyal niches within the world's deepest lake. Baikal Oilfishes (Comephorus spp.) represent a highly apomorphic taxon with unique skeletal morphology, soft anatomy, and reproductive ecology. Selection for novel behavior and life history may be evident in genes responsible for organismal energy balance, including those encoding subunits of the electron transport chain. Complete mitochondrial genomes were sequenced for the Big Baikal Oilfish (Comephorus baicalensis) and Little Baikal Oilfish (Comephorus dybowskii). Mitochondrial genomes encode genes essential for electron transport, and data provided here will complement ongoing investigations of genome-to-phenome maps for teleost respiration and metabolism. Phylogenetic analyses including oilfish mitogenomes and all publicly available cottoid representative sequences are largely concordant with previous studies.
ABSTRACT
Studies over the past decade have shown a significant role of synonymous mutations in posttranscriptional regulation of gene expression, which is particularly associated with messenger RNA (mRNA) secondary structure alterations. Most studies focused on prokaryote genomes and the nuclear genomes of eukaryotes while little is known about the regulation of mitochondrial DNA (mtDNA) gene expression. This paper reveals signs of selection in synonymous sites of the mitochondrial cytochrome b gene (Cytb) of Baikal oilfish or golomyankas (Comephoridae) directed towards altering the secondary structure of the mRNA and probably altering the character of mtDNA gene expression. Our findings are based on comparisons of intraspecific genetic variation patterns of small golomyanka (Comephorus dybowski) and two genetic groups of big golomyanka (Comephorus dybowskii). Two approaches were used: (i) analysis of the distribution of synonymous mutations between weak-AT (W) and strong-GC (S) nucleotides within species and groups in accordance with mutation directions from central to peripheral haplotypes and (ii) approaches based on the predicted mRNA secondary structure.
Subject(s)
Cytochromes b/chemistry , Cytochromes b/genetics , Nucleic Acid Conformation , RNA, Messenger/genetics , Animals , Mitochondria/enzymology , Perciformes/genetics , RNA, Messenger/chemistryABSTRACT
Sympatric speciation was studied in two sister species of cottoid fish from Lake Baikal (East Siberia): big golomyanka or Big Baikal oilfish (Comephorus baicalensis Pallas, 1776) and small golomyanka or Little Baikal oilfish (C. dybowski Korotneff, 1905). Analysis of nucleotide sequences of mitochondrial cytochrome b gene showed that the Little Baikal oilfish (LBO) formed a single population in the lake, whereas the Big Baikal oilfish (BBO) was divided into two genetic groups - BBOI and BBOII, which were not separated geographically. Phylogenetic analysis showed that BBO is a more ancient species than LBO and that the paraphyletic origin of LBO is from the BBO genetic lineage within the genus Comephorus. Population-genetic structure and phylogenetic relationships between the two golomyanka species are considered to be a consequence of paleoenvironmental events that took place in the Baikal region during the past hundreds of thousand years.
