The State of Gonads of Spawners of Whitespotted Char Salvelinus leucomaenis, Northern Dolly Varden S. malma, and Whitespotted Char × Dolly Warden Hybrids from the Utkholok River in the Light of the Problem of Interspecific Hybridization in Chars of the Genus Salvelinus (Salmonidae)

Abstract

Macro- and microscopic studies of the state of the gonads of spawners of whitespotted char Salvelinus leucomaenis, Dolly Varden S. malma, and whitespotted char × Dolly Varden hybrids from the Utkholok River (northwestern Kamchatka) in the post-spawning period have revealed no anomalies in the structure of the gonads and their cytological state. The generative tissue of the testes and ovaries contained germ cells of subsequent generations, which indicates the capability of post-spawned individuals for repeated maturation and reproduction in the next year. The state of the gonads of hybrid individuals fully corresponds to that of polycyclic salmon fishes (Salmonidae) and does not differ from the parental species, whitespotted char and Dolly Varden; their gametogenesis has no visible deviations. This indicates the potential capacity of the hybrids from the Utkholok River for reproduction and maintaining their own population, in contrast to many other cases of interspecific hybridization in salmonids described in the literature. The resulting data on the state of the gonads and the results of the previous genetic analysis of hybrids indicate an important feature of the “Utkholok River” hybrid zone for chars of the genus Salvelinus, such as the transition of the entire system to the state of the so-called “hybrid swarm.” This may lead to a scenario when hybrids can move to the next stage of microevolutionary processes, which will lead to their isolation from the parental species.