Developmental table of the early mouse post-implantation embryo.

The developmental tables of early somite mouse embryos that are presently available from the literature give clear and useful descriptions of the differentiation at successive stages. However, they provide no easy access to the correlation between the growth of the embryo and its differentiation. In the present study, quantitative data concerning normal mouse embryonic development as well as the major developmental events occurring between 0 and 30 pairs of somites were established. Measurements of growth (crown-rump length, head length, absorbancy at 280 nm) and differentiation parameters (morphological score) of 168 to 310 explanted mouse embryos were recorded for each developmental stage (number of pairs of somites). A short description of the major events occurring at the corresponding stages is also presented. The table is more detailed than those presently available and provides a rapid and practical overview of the timing of the appearance of developmental events and differentiation in correlation to the progressive growth of the embryo. It could, therefore, be useful for embryologists and toxicologists. In addition, the development of 67 post-implantation mouse embryos cultured in vitro was compared with the reference table established from in vivo embryos. Our results confirm and extend previous reports showing that embryos cultured in vitro grow and differentiate at a pace very similar to that of embryos developed in vivo.