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The evolution of reproduction in marsupials, and speculation about the ancestral state of mammalian reproduction, have engaged discussion since the end of the 19th century. Both sexes possess a cloaca , [ 17 ] although modified by connecting to a urogenital sac and having a separate anal region in most species. [ 18 ]
As marsupials, female opossums have a reproductive system that includes a bifurcated vagina and a divided uterus; many have a pouch. [29] The average estrous cycle of the Virginia opossum is about 28 days. [30] Opossums do possess a placenta, [31] but it is short-lived, simple in structure, and, unlike that of placental mammals, not fully ...
Marsupials' reproductive systems differ markedly from those of placentals, [10] [11] though it is probably the plesiomorphic condition found in viviparous mammals, including non-placental eutherians. [12] During embryonic development, a choriovitelline placenta forms in all marsupials.
Like all female marsupials, the female's reproductive system is bifid, with two lateral vaginae, uteri, and ovaries. [45] The male's penis is also bifid, with two heads, and as is common in New World marsupials, the sperm pair up in the testes and only separate as they come close to the egg. [45] Males have three pairs of Cowper's glands. [46]
Being a marsupial and at the same time an aquatic animal, the water opossum has evolved a way to protect its young while swimming. A strong ring of muscle makes the pouch (which opens to the rear) watertight, so the young remain dry, even when the mother is totally immersed in water. [ 6 ]
Like all marsupials, gestation is probably short, with females' giving birth to poorly developed young and most of the development taking place during lactation. [5] It is likely that reproduction is similar to that of Marmosa robinsoni, which gives birth to 6–14 young after a gestation period of just 14 days. The tiny young, measuring only ...
The common opossum (Didelphis marsupialis), also called the southern or black-eared opossum [2] or gambá, and sometimes called a possum, is a marsupial species living from the northeast of Mexico to Bolivia (reaching the coast of the South Pacific Ocean to the central coast of Peru), including Trinidad and Tobago and the Windwards in the Caribbean, [2] where it is called manicou. [3]
It was the first marsupial to have its genome sequenced. The gray short-tailed opossum is used as a research model in science, [4] and is also frequently found in the exotic pet trade. It is also known as the Brazilian opossum, rainforest opossum and in a research setting the laboratory opossum.