Complete mitochondrial genomes of Baikal endemic coregonids: omul and lacustrine whitefish (Salmonidae: Coregonus sp.).

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.

The synthesis and crystal structure of 2-(chloro-selan-yl)pyridine 1-oxide: the first monomeric organoselenenyl chloride stabilized by an intra-molecular secondary Se⋯O inter-action.

The title compound, C5H4ClNOSe, is the product of the reaction of sulfuryl chloride and 2-selanyl-1-pyridine 1-oxide in di-chloro-methane. The mol-ecule has an almost planar geometry (r.m.s. deviation = 0.012 Å), and its mol-ecular structure is stabilized by an intra-molecular secondary Se⋯O inter-action of 2.353 (3) Å, closing a four-membered N-C-Se⋯O ring. The title compound represents the first monomeric organoselenenyl chloride stabilized intra-molecularly by an inter-action of this type. The non-valent attractive Se⋯O inter-action results in a substantial distortion of the geometry of the ipso-carbon atom. The endo-cyclic N-C-Se [102.1 (3)°] and exo-cyclic C-C-Se [136.9 (3)°] bond angles deviate significantly from the ideal value of 120° for an sp2-hybridized carbon atom, the former bond angle being much smaller than the latter. In the crystal, mol-ecules are linked by C-H⋯O hydrogen bonds, forming zigzag chains propagating along [010]. The chains, which stack along the a-axis direction, are linked by offset π-π inter-actions [inter-centroid distance = 3.960 (3) Å], forming corrugated sheets parallel to the ab plane.