Histological analysis of implantation embryos in large Japanese field mouse (Apodemus speciosus) and estimation of developmental stage.

The large Japanese field mice (Apodemus speciosus) are small rodent specie endemic to Japan. The genetic characteristics of A. speciosus is different chromosome numbers within one species. Furthermore, A. speciosus is used for research in radiation and genetics. In this present study, a pregnant A. speciosus was obtained, and histochemical analysis of the implanted embryos was performed and compared with developmental stages of the mouse. Although there were some differences, the structures of the implanted embryos including the primitive streak and placenta of A. speciosus were similar to that of the mouse. Our study will be important report in the construction of a developmental atlas of A. speciosus.