Structure of "species flocks" in fishes: Channels of the splanchnocranium divergence in endemic lacustrine benthivorous charrs (Salvelinus, Salmonidae, Teleostei) in Lake Kronotskoye, Kamchatka.

The structure of splanchnocranium bones has been studied in four endemic benthivorous charrs (the genus Salvelinus) from Lake Kronotskoe (Kamchatka). It has been found that, according to the whole set of characters of the splanchnocranium structure, the most expressed differences are observed between specialized forms, nosed and largemouth charrs, inhabiting different biotopes of the lake. Differences between small-mouth and white charrs are less pronounced, and the species are characterized by generalized features of the structure of jaws. It can be suggested that, in addition to diverse feeding preferences within a feeding niche, an extremely high diversity of charrs in Lake Kronotskoe is due to a complex geomorphological structure of the water system. Thus, the "species flock" comprising a complex set of diverse benthivorous morphotypes has been formed and exists in Lake Kronotskoe. Charrs from Lake Kronotskoe are a representative example of sympatric speciation by way of formation of new forms differing from each other in morphological, ecological, and trophic features.