Do female marsupials give birth through a cloaca or do they have a separate vaginal opening like placentals?

Submitted by Pe45nira3 t3_1190htj in askscience

When searching for this information online, I found contradictory answers. I know that marsupials, in contrast to placentals both urinate and defecate through a cloaca like reptiles do. However when I tried searching for whether female marsupials' vagina also opens into the cloaca or whether there is a separate opening for it, one site seems to suggest the former, the other the latter.

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sighthoundman t1_j9nftdf wrote

Oh, boy do they have a separate vaginal opening.

There is variation, but the basic plan is that the male has a bifurcated penis. The female has two lateral vaginas, each leading to it's own uterus. In addition, there's a median vagina that opens into near the pouch (marsupium, which gives them their name) and that the babies must crawl from that opening to the pouch immediately* after birth, when they are just feet and lips*.

I rate the Wikipedia article on marsupials essentially accurate. Not worth the time and effort to clean up.

* Eh, close enough.

Edit: eliminated some false facts.

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Peter_deT t1_j9nyzle wrote

The central vagina (used for birth) does not open into the pouch, Typically the mother licks a path from the vagina to the pouch and the new-born crawls along it, into the pouch and latches on to a teat.

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Justadumbuser t1_j9nxflg wrote

So they have 3? Evolution is definitely inventive.

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djublonskopf t1_j9orcrt wrote

Placental mammals (like us) basically start with 3 precursor tubes that fuse together early in development.

In marsupials, the ureters (which transport urine from kidneys to the bladder) pass in between the 3 vaginas, so it would be pretty much impossible for them to fuse without cutting off the transport of urine to the bladder. In placental mammals, the ureters develop differently and no longer pass between the tubes, which is why it's possible for us to fuse the 3 precursor tubes into one.

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NedRyerson_Insurance t1_j9of2je wrote

Is there any difference between marsupials whose pouch opens upward or downward? Are they anatomically the same aside from that switch?

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Any-Broccoli-3911 t1_j9ofeqv wrote

They have 3 vaginas, but the 3 vaginas are inside the cloaca, so there is only one external opening.

The penis is two-pronged to penetrate both lateral vaginas at the same time, though typically only one is fertile at a time. The penis is also inside the cloaca while not erect.

They also have 2 uteri.

The middle vagina is for the baby to leave any of the uteri, and then the baby leaves the body by the cloaca and then gets into the pouch.

https://trishansoz.com/trishansoz/animals/marsupial-reproduction.html

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Lt_Mashumaro t1_j9nom0c wrote

You may have already found this website, but in case you haven't, here it is! I learned quite a lot from it. It seems like the cloaca is the "one hole for everything" including breeding, even in kangaroos.

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