Ecology


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Australian Marsupials
American Marsupials
Ecology
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Sexual Reproduction and Development

Introduction.

Male Reproductive System.

Female Reproductive System
The female reproductive system is generally similar to the placental system, although it does have more differences than the male systems. There is also a larger variation in size and shape between different marsupial species, although all share the same basic morphology.

There are 2 ovaries, each with a cortex containing oocytes, or egg cells. Leading from these ovaries are the oviducts, usually the location of fertilisation of an egg. The oviducts lead into 2 uteri with separate cervices, which both lead down into a single anterior vaginal expansion. From this vaginal expansion 3 separate vaginae, 2 lateral and 1 median, or 'pseudovagina', split apart. They rejoin to enter a single urinogenital opening, called the cloaca. This major difference in vaginal morphology from placentals comes from a difference in embryonic development; in placentals, the uteri and vaginae of each ovary fuse to form a single uterus and vagina, whereas in marsupials they do not fuse during development.

female repro (16K)
Comparison of Marsupial and Placental Reproductive System

The female ovulation cycle is also very similar to that of placentals, with a number of oocytes developing each within a ball of cells, called a follicle. As the follicle matures in the ovary, a fluid filled cavity forms, pushing the oocyte to one side. At ovulation, the wall of one or more follicle bursts, releasing the egg into the oviduct. The remains of the follicle develop into the corpus luteum, which controls the majority of processes throughout any following pregnancy. The egg is swept down the oviduct by ciliary action, and it is here it will be fertilised if mating has occurred. The egg, whether fertilised or not, passes into one of the uteri within 24 hours of ovulation. If fertilisation has occurred, then the egg will plant itself in the wall of the uteri and begin to develop into an embryo.

Seasonal Breeding.

Pregnancy, Birth and Diapause.

Lactation.