Culture of Marsupial Oocytes and Conceptuses

: Marsupial oocytes and conceptuses provide special challenges to scientists wanting to develop reliable in vitro techniques. Yet these techniques are essential to the study of development. Such techniques also provide tools to help prevent further decline in marsupial biodiversity using assisted reproductive technology. Specific marsupial characters have made development of in vitro techniques difficult. Some of these are the high-energy requirements of cleavage and blastocyst formation and maintenance because of cell-zona adhesion; the essential nature of the shell coat for most of development; the prevalence of embryonic arrests in vivo and in vitro during cleavage and unilaminar blastocyst stages; and the fragility of blastocysts leading to precocious shell loss and developmental failure in vitro. The advantages of marsupial culture during development are that the gestation period is very short, that the implantation is superficial in many, and that the neonates are altricial. This chapter outlines solutions to some of these problems in a representative, polytocous, dasyurid marsupial, Sminthopsis macroura. It is a natural superovulator with the shortest gestation period of any mammal, which has been cultured to within 5 h of birth. The other representative marsupial, the monovular phalangerid Trichosurus vulpecula, has a very superficial implantation that allows vesicles to readily detach from the endometrium.