Mechanisms and frequency of nuclear divisions in trophoblast and decidua cells during postimplantation embryogenesis in the mouse

The finding of amitotic division of trophoblast cell nuclei in blastocysts of the American mink (Mustela vison), which has an obligatory period of delay in implantation (obligatory embryonic diapause) in its ontogenesis, led us to study the mechanisms and frequencies of division of trophoblast and decidua cell nuclei during the postimplantation embryogenesis of mouse (Mus musculus), which does not exhibit an obligatory diapause nor amitosis in blastocysts. It has been established that the main mechanism underlying the cell nuclei division in both tissues (trophoblast and decidua) forming the placenta is amitosis. These data suggest that the occurrence of an obligatory embryonic diapause in ontogenesis of certain animal species is related not only to the delay in implantation, but also to the alteration in the chronology of all processes of embryogenesis.