Can marsupial mammals mate with placental mammals?
January 03, 2011 3:12AM
No, they cannot mate. The reason for this is way the fetus develops in each animal is very different. The placental mammal fetus grows and matures within the mother's uterus for the entire pregnancy, obtaining nourishment from the placenta. When the infant is born, it is fully formed and can survive outside the womb. Marsupial fetuses exit their mother's body when they are very tiny and at a primitive stage of development and then make their way up the mother's abdomen and into the pouch (or, in some cases, a mere flap of skin), where they will latch onto the mother's teat for nourishment while they continue to mature and grow until the infant marsupial is able to survive outside the pouch. The teat actually swells in the embryo's mouth, securing it in place.
Marsupials have very different reproductive systems to that of placental mammals. Female marsupials have two vaginas, or what are called paired lateral vaginae. These are for the purpose of transporting the sperm to the womb, but there is a midline pseudovaginal canal for actually giving birth. As well as two vaginas and two uteruses, female marsupials have two fallopian tubes and two cervixes. Most male marsupials, with the exception of the largest species, the Red Kangaroo, Eastern Grey and Western Grey Kangaroos, have a two-pronged penis to accommodate the females' two vaginas.