Morphology of genitals and copulatory behavior in social voles of the subgenus Sumeriomys (rodentia, arvicolinae)

The structure of genitals and copulatory behavior in eight forms of social voles of the subgenus Sumeriomys are described. The morphology of the male penis mainly of a conservative structure, but it may vary essentially is some details, the direct correlation between the morphology of genitals in male and female is observed. Nonetheless, individual variability is considerable, and it can overlap both interspecies and subspecies variation. Some vole subspecies differ to a lesser degree than species. The diversity of male genitals is suggested to be a result of affecting genes. Genital morphology varies in accordance with other characteristics (for instance, body length). Genitals cannot serve as a mechanism of mechanical isolation. The structure of male genitals does not correlate with specific features (numbers of ejaculations, intromissions and thrusts per test) of copulatory behavior. Mating stimulation is necessary for fertilization, ovulation, and implantation in females. It is probably the main biological effect of structural and physiological evolution. It is concluded that the divergence of social voles in genital structure and copulatory behavior does not promote the formation of insulating mechanisms that prevent their death.