Early differentiation of the gonads in the gray short-tailed opossum (Monodelphis domestica).

The time course for gonadal development in gray short-tailed opossums was examined in this study. It was found that the gonads were not differentiated on day 1 of postnatal life (the day of birth). While testis development was seen by postnatal day 4, ovarian development did not occur until after postnatal day 16. In both sexes, primordial germ cells were not identified until after postnatal day 1. These findings are discussed with respect to gonadal differentiation in other marsupial species.