Comparative study of developmental progress in the mouse, rat and rabbit in their stage of organogenesis

Abstract

1. Comparative developmental stages in the CF#1 mouse, S.D. rat and Japanese white rabbit were examined under the same condition as when teratogenicity tests will be carried out. The developmental phase in presomite embryos, somite number, development of the eye and forelimb were taken as criteria so as to estimate the developmental stage of each species of animals employed. 2. Individual variation in development, progress of development, and corresponding stage of development were compared among the three species of animals. 3. Individual variation in development was the most apparent in the mouse, the next in the rabbit and the least in the rat. 4. Progress in development in the three species of animals examined was different according to the criterion adopted. Progress in development seen from the somite number was similar in the mouse and rat and progress was even constant. In the rabbit, progress in development in the first half period of organogenesis was similar to that in the mouse and rat. Thereafter, progress of development was slower than that in the mouse and rat. 5. Somite counts showed that developmental stages of day 8, 9, 10, 11 and 12 in the mouse corresponded to those of day 91/2, 101/2, 111/2, 121/2 ar,d 131/2 in the rat and to those of day 711/2, 81/2, 911/2, 11 and 12 in the rabbit, respectively. However, when the development of the eye was taken as a criterion, developmental stages of day 10, 11, 12 and 13 in the mouse corresponded to those of day 111/2, 121/2, 131/2 and 141/2 in the rat and to those of day 10, 11, 12 and 13 in the rabbit, respectively. As far as the development in the forlimb, developmental stages of day 10, 11, 12 and 13 in the mouse were equivalent to those of day 111/2, 121/2, 131/2 and 15 in the rat and to those of day 11, 12, 13 and 15 in the rabbit, respectively.