Egg production

[ConcinusMan]

Sorry Le Ann, I didn't see your post before I added that last sentence. I'm still not sure if garters have a vascular connection to the developing eggs yet, but if they do, and they are truly ovoviviparous animals, then that connection is needed or the eggs will not be able to get the necessary gas exchange needed if they are removed from the mother prematurely. I think that's what happens when you find fully and normally developed young being born dead. I think what happens there is that the connection needed for gas exchange happens prematurely and the young basically suffocate before they are able to resume breathing on their own. If we could test the dead young in the lab and find that their blood is high in Co2 and low oxygen, that would all but confirm the hypothesis.

Removing them from the mother would be like ripping the shell and shell membrane off of a chicken egg and expecting the embryo to live. You would essentially be doing the same thing if you placed a whole chicken egg in an oxygen depleted atmosphere. The young inside the egg would suffocate.

[guidofatherof5]

Then why the need for a yolk Steve? You've seen them born enough times to see it's obvious the umbilical cord is attached to the yolk just like any other egg.

I believe there are other connection as in small blood vessels that aid in the development.
Has anyone done an necropsy on a gravid female? It may not be something that is seen with the naked eye.
I've just seen too much eating for it to just be for next years development.
Whatever the answer, a gravid females nutritional intake is important and should be made optimal to enhance the young's eventual outcome.
Just my opinion.

[ConcinusMan]

I've just seen too much eating for it to just be for next years development.

If you just gave up a good portion of your stored mass to produce yolks and albumen for the growing offspring, you would be hungry too. It stands to reason that they would need to get started on that right away if they are to replenish enough before winter sets in.

You keep saying it's an opinion Steve but there are facts in question. They are either ovoviviparous, and the growing embryos get their nutrients from the yolk, or science has been wrong all along and they are not ovoviviparous after all. There are plenty of studies done that prove the mother does not supply the nutrients directly but places them in the yolks over time in preparation. This was proven on red sided garters as well as T. radix and T. ordinoides. This thing about the calcium.. that's one mineral, that is not fat and protein, which makes up a majority of the mass needed for embryos to develop. There are obvious advantages to this.

I still say if there's any circulatory connections between the mother and the membrane during gestation, it is strictly for gas exchange. The mother and the offspring have independent circulatory systems. They are not directly connected in ovoviviparous animals. The connections aren't even needed for fluids to enter the membrane. They are there to connect to the membrane so the mothers blood can take away Co2 and provide oxygen and that's about it. Once those embryos are growing, the only thing mom does for the young is thermoregulation and she does their breathing for them. Her lung does the work until the embryos are mature.

It's not an opinion. These are the facts of ovoviviparity.

[guidofatherof5]

Yes I understand.
I was simply exploring what I had observed and always stated it was just my opinion.
I'm not trying to call into fact that the studies are wrong.
Just speaking from a layman's point of view.

[ConcinusMan]

Well obviously I'm a layman too. Just trying to explore how this works and try to understand it better. If that's going to happen I want to make sure that it is understood correctly. Not just by me, but anyone else who cares to read the thread. I started the thread mainly because I see so many people here on the forum that know a lot about snakes, but when it comes to understanding their ovoviviparous reproduction, they just don't have it right.

[mb90078]

What about the fact that it requires more energy for the mother to carry this extra "dead weight" around? Might that not account for a good portion of the extra consumption?

[ConcinusMan]

That's a good thing to consider but I have doubts that the little bit of extra weight has enough of an impact to have an influence on the food intake. Other than very limited movement mainly to thermoregulate, I don't see any of my captive gravid snakes doing much moving at all so there's not much "carrying around" going on. I think it has more to do with the need to replenish what she has given of herself (mass and nutrients) in order to produce eggs before they were fertilized, then secondary, after the babies are born, to start growing new ones for the next time.

[gregmonsta]

I still say if there's any circulatory connections between the mother and the membrane during gestation, it is strictly for gas exchange. The mother and the offspring have independent circulatory systems. They are not directly connected in ovoviviparous animals. The connections aren't even needed for fluids to enter the membrane.

Some more tidbits from the paper I found on the females contribution via the placental membrane - placental provision of water and sodium both exceed what is in the yolk supply.

^^ .... there's the fluid exchange + an extra mineral. In both cases more than what is present in the yolk (increasing the initial yolk resevoir by more than a factor of 2).

Yolk = principal source of organic nutrition
Placental contribution of base elements + water = continued investment in both growth, bone develpment, additional requirements for metabolisis, etc.

[ConcinusMan]

I'll buy that. There just wouldn't be enough room in her for all that fluid to be stored initially in the egg and still have room for the embryos to grow. Since shes holding them for development, that wouldn't be necessary anyway. It's interesting that calcium is supplied during gestation. I mean, when a bird lays their egg, calcium is used to form the hard shell after fertilization.

Anyway, the thing that was trying to drive home when I started this thread is "Yolk = principal source of organic nutrition". The fact that the yolk reserve is growing months in advance, and no longer growing after fertilization, still suggests that after fertilization, the food she is receiving is not for the young she is currently carrying. They already have what they need stored in the yolks.