Formation of extratropical (moderately cold-water and bipolar) ranges of species of mesopelagic fish of high-latitude areas of the world ocean

Ichthyofauna of mesopelagial of high-latitude areas in the World Ocean is considered in the paper on the basis of taxonomic reports and revisions of recent years. Different degree of endemism of mesopelagic ichthyofauna in different high-latitude areas of the World Ocean is recorded. The South Ocean and the northern Pacific are characterized by the highest degree of endemism at generic and species levels. Hypothesis of the earliest (Oligocene-Miocene) time of formation of high-latitude ichthyofauna of the pelagial of the South Ocean is advanced. In the northern hemisphere, high-latitude areas of the northern Pacific are characterized by the earliest time of formation of pelagic ichthyofauna—presumably the Miocene-Pliocene. Ichthyofauna of the mesopelagial of the North Atlantic has the youngest age: Pliocene-Pleistocene. Bipolarity of high-latitude ichthyofauna of mesopelagial was considered. Maximum number of common (identical) pairs of species (14) inhabits the northern Atlantic and the South Ocean. The South Ocean and the northern Pacific are characterized by minimal number of common pairs of species (3). The remaining bipolar taxa are represented mainly by more or less closely related species of specific high-latitude genera, whose number in the South Ocean is greater than in the northern Atlantic and Pacific. On the basis of data of paleooceanology of the Cenozoic period, the hypothesis of formation of bipolar taxa and their ranges in connection with change in configuration of continents, oceans, and climate change is considered.