Oolon Colluphid

Thanks! Yup, the new addition to the list presently says:

• Penguin eggs. Echidnas lay eggs too . . . and put them straight into their pouches. One might think that if a pouch is a Good Idea™ for an egg-laying thing, that it would save birds having to fanny around with nests. Ah, you’ll say, but birds have to fly, and having a nestfull of eggs or chicks in a pouch would make flight difficult. Sure . . . but not for flightless birds! This is especially relevant for penguins.
  
  Penguins, like every other bird, need to keep their eggs warm. Living in the silly places they do, however, means they can't have a nest (made of what -- shaved ice?). Instead, the poor little buggers have to sit the egg on their feet and cover it with a flap of groin skin. When they do this, they can hardly move, and they have to swap it over to other penguins if they want to go and grab a bite to eat, which often involves rolling it along the ice. This is a dangerous way of warming an egg. Imagine how much easier it would be for them to have that flap of skin surrounded with contractile muscles, like a marsupial pouch between its legs. If it was really good at sealing (with some sort of glands producing water-resistant mucous?), then the bird could even take the egg with it swimming for food. There is no questioning that a better developed pouch would be useful to penguins, given that they try as hard as they can to have one anyway.
  
  And, a sealable pouch design was known to the Creator, because he used it in the yapok (water opossum, Chironectes minimus). But . . . but . . . the eggs might get broken! So, uh, how about having live young?
  
  http://www.press.jhu.edu/books/walke...ironectes.html

Oolon

Doubting Didymus

Does this mean I get a footnote in your reference list?

Albion

Say penguins did have pouches - how would they get the eggs into them? They don't have useful arms or legs or long enough necks to manipulate eggs into a pouch, do they? What sort of mechanism of getting the egg from the outside world into the pouch were you thinking of, DD?

Doubting Didymus

Easy. penguins very nearly do have pouches, as I mentioned before. They sit the egg on their feet and cover it with a flap of groin skin. I imagined that very selfsame flap, with a few muscles here and there, could seal up nicely.

Perhaps you were imagining the pouch on the front belly of the penguin, like marsupials? If that were the case, then Oolons idea of having the egg / child laid directly into the pouch would solve it, and there's no real reason why penguins shouldn't be able to have their young live anyway.

Duvenoy

The shell does indeed begin to form, but it never gets beyond the stage of being a membraneous sac. The neonate is born in this sac and must break out of it as if it were a shell, an easy way to enter the world as compared to, say, turtles and people.

Side note: I remember my grandmother butchering a hen, many years ago (I got stuck with plucking it ). As she gutted it, there was a quanity of eggs inside. I recall seeing that only a couple had shells and the rest looked like blobs of yoke, of varing size.

I didn't know echidnas could curl up and deposit their egg in their pouch! How amazing!

doov

Duvenoy

Let me clean the above up a little (I was in a hurry).


In an ovoviviperous serpent, the egg forms in the usual way, except the shell never fully develops. The female retains her young through their entire development, and that development takes place in the membrane that would be the shell in an egg-laying species. The neonate is born, a miniture of it's parents and ready to fend for it's self, as soon as it breaks free of the membrane (shell), which contained it at birth.

doov

reprise

If you want to know more about some of the more bizarre ways in which nature has evolved to protect developing creatures during gestation, check out the Surinam Toad, Darwin's Frog, and the Gastric Brooding Frog.

Mallee Fowl are pretty good at ensuring the safety of their eggs, too.

Duvenoy

Thanks reprise! Pipa pipa is my all-time favorite amphib. I once kept a pair in an aquarium.

Might also look up whip tail lizards for yet another remarkable reproduction strategy. Parthenogenisis, if I've spelled that right. I'd post links, but I just got home from an MC meeting and an a little too loaded to dig them out. Sorry!

doov