[Embryonic mortality of the root vole as an index of the effect of small doses of natural radioactivity on genetic processes in populations].

A study was made of the pre- and post-implantation death of (F2--F4) Microtus oeconomus progeny whose parents lived in territories where natural radiation background was increased (an exposition dose-rate of 3.6-144.0 pC/kg X s). The spontaneous rate of pre- and post-implantation death of progeny of irradiated (experimental) animals was higher than that of intact ones (control). The animals kept in conditions of chronic irradiation (46.2 pC/kg X s) exhibited a more pronounced discrepancy in embryonal death rate. It is suggested that genetic differences in the populations were responsible for different rate of embryonal death of the control and experimental animals.