Prenatal neurogenesis in the telencephalon of the precocial mouse Acomys cahirinus

[³H]thymidine autoradiography was employed to examine the times of formation of the major neuronal classes in the forebrain of the precocial mouse Acomys cahirinus. Dams received 3 thymidine injections over a 24 h period on either embryonic Day 14, 18, 20, 22, 29 or 36. Age-related changes in the distribution and number of heavily labeled cells were noted. Acomys exhibited later onset and more protracted periods of cell generation than the phylogenetically related, altricial laboratory rat or mouse, indicating considerable differences in patterns of early growth between the species. Understanding the factors responsible for these differences could lend important insights into evolutionary mechanisms involved in the process of speciation.