Monodelphis whole-embryo culture

INTRODUCTIONMonodelphis domestica, the gray, short-tailed, or laboratory opossum, is the most commonly used laboratory marsupial. In addition to the factors that make it a convenient laboratory animal (small size, ease of care, nonseasonal breeding), it is the first marsupial whose genome has been sequenced. Monodelphis has proven useful as a model organism for studies on spinal cord regeneration, ultraviolet (UV)-induced melanoma, and genetic influences on cholesterol, as well as comparative studies of the immune system. In addition, Monodelphis has been used to understand the basic functions of the olfactory system and the role of various olfactory chemicals in social and reproductive behavior. Recently, Monodelphis has been used to understand fundamental aspects of marsupial development, anatomy, evolution, and evolutionary consequences of the derived marsupial mode of development and reproduction. The embryos of Monodelphis, like those of other marsupials, can be cultured in vitro. The length of embryo viability depends in part on the stage at which culture begins, but embryos of different species of marsupials have been cultured for 18 h to almost 72 h. Good culture results for Monodelphis have been obtained using the method presented here. Embryos can be manipulated and then placed in the incubator. We have applied this technique most commonly to embryos at stages 23-25; they have retained viability and normal development through stage 26 when embryos would begin to implant in vivo.