Egg production

[ConcinusMan]

I have noticed on multiple occasions, I get the impression that there is a general tendency for people to think that their female is "eating for two" (dozen) while she is gravid and that somehow the nutrition, food resources, frequency, etc., she gets during this time somehow benefits the health of the young. I can't seem to find a reason why it would. Snakes are not placental mammals!

After all, that would be like saying a chick benefits from nutrients taken in by the hen AFTER the egg is fertilized and/or laid. That obviously doesn't happen.

I've been reading some things during the past few days. Specifically, research on garter snake reproduction. The studies seem confirm what I always suspected. The mass (all the necessary resources) that goes into making those unfertilized eggs and the nutrients they contain for the young, are acquired by the mother during the period of time before the eggs begin to form inside her and possibly also while the eggs are forming. Maybe this is why you don't see significant weight gain before conception or ovulation?

I mean, that's when the "eggs" are forming inside her, getting bigger each day leading up to maturity and which point they will only then be ready for fertilization, yet there's no weight gain until after ovulation and conception. Why is that? The answer is that she is merely shifting mass from herself and putting it into making eggs perhaps. That means she acquired the resources (mass) for those eggs long before the young are even conceived and long before ovulation occurrs.

Once she ovulates, she no longer has any connection to, or any contribution to the resources contained in that egg (other than gas exchange and water) so a gravid girl is then eating for herself and next season's young, not the current one's she's carrying.

Am I wrong? am I thinking correctly here?

[Stefan-A]

Capital breeding, income breeding. Those are two terms worth looking up.

[ConcinusMan]

OK, I read enough to get the general gist of it. The main point I wanted to make is that the nutrients stored in each snake egg is capital from the moment of conception. Is it not?

Granted, garters may or may not use a combination of both strategies until the ovocytes are mature but once they are mature and become fertile eggs, they are now stored energy (captial) for the offspring. Perhaps I'm oversimplifying, I don't know. That's why I posted. I need feedback so I can hopefully understand it better.

[gregmonsta]

It's what I was getting at, to a point, in one of my earlier threads about the conversion of source material (fat/protein stores and food intake) into a denser/heavier material.
On another note - studies have also shown that some source materials, specifically calcium, are supplemented from the mother via the placental membrane.

[MasSalvaje]

I had this same question not too long ago and the response I got was that is is not completely one or the other. The speculation is that there is a lot more "interaction" going on between mother and eggs that was not previously thought of. There are some studies that are being done to determine those interactions if they are really going on. Greg mentioned the Ca example, they think there may be others as well. For this very reason the term Oviviparous has been debated about as well.

-Thomas

[ConcinusMan]

But then there's the argument about mass. While source material can be converted to denser material, it stands to reason that the amount of mass, or total weight of the converted material should not exceed that of the source unless additional material is being added during the conversion process. Furthermore, it seems to me that the converting itself would have a metabolic cost (overhead) which may or may not be covered by food taken in during the conversion process.

Speaking strictly about the period of time it takes for the ovocytes to grow to mature ova (in the months prior to ovulation and/or fertilization) which would be fall through spring fertilization in the wild, you just don't see the snake gaining significant weight. Certainly not enough to account for the mass of the mature ova that have been growing in her during that time. That tells me that at the majority of the material used to create those mature ova likely comes from her own body and/or food intake during the period of time prior to actual ovulation and fertilization. If that assumption is true, then it stands to reason that the majority of the material needed to produce that litter, was gained over time and stored by the mothers body, long before the ova began to grow.

In other words, the food she took in last summer after ovulating is the main source for the current litter. Any material taken in after ovulation benefits and replenishes the mother, and is stored in her body for the next years litter.

Controlled experiments confirm that having plenty of extra food during the gestation period has a direct effect on the mothers mass after the babies are born, but has no effect on the health, size, and mass of the litter inside her. I think this is why sometimes wild snakes skip having litters in some years and do not produce ova or at least, do not have enough resources to bring them to maturity in time for spring mating season.

If food resources were bountiful last summer, then that food resource would have an influence on the health, mass, and numbers of young born the following spring.

I guess my point is that having a healthy snake with good mass and nutritional intake at all times of the year is what makes for healthy litters. Other than perhaps a little extra calcium, it doesn't take extra food mass or high nutrition during pregnancy to make for a healthy litter. What really mainly matters for the current litter is the resources that were available to the mother prior to ovulation.


. The speculation is that there is a lot more "interaction" going on between mother and eggs that was not previously thought of. There are some studies that are being done to determine those interactions if they are really going on. Greg mentioned the Ca example, they think there may be others as well. For this very reason the term Oviviparous has been debated about as well.

-Thomas

I'm with you on this one. Seems to me that the amount of mass gained during gestation cannot be accounted for by gas exchange and calcium intake of the unborn young alone. The mass gained by the growing young inside her can't be coming from the ova either since they reached full mass before ovulation. Still a mystery to me why they gain so much weight during gestation. That mass has to come from somewhere.

EDIT: I did just think of another source for the mass gain. Obviously the young won't develop without warmth. Warmth is energy. Is the weight gained during pregnancy by converting thermal energy to mass as the young develop? Plants do this as they grow, do they not?

[guidofatherof5]

After all, that would be like saying a chick benefits from nutrients taken in by the hen AFTER the egg is fertilized and/or laid. That obviously doesn't happen.


Once she ovulates, she no longer has any connection to, or any contribution to the resources contained in that egg (other than gas exchange and water) so a gravid girl is then eating for herself and next season's young, not the current one's she's carrying.

Am I wrong? am I thinking correctly here?

I'm not sure the chicken example is a good one. Obviously those eggs are void of the mother once they are layed
Garter snakes are attached to the eggs. The blood that flows into these babies is carrying nutrients that the mother has consumed.
Her nutritional input must benefit them in some way. I don't believe this egg chain is a self sufficient mass inside the Mother. Her health has a great in-pack on these babies.
This voracious appetite that occurs can't be for next years litter only.
Just my opinion.

[gregmonsta]

Well put, but with this - "Other than perhaps a little extra calcium, it doesn't take extra food mass or high nutrition during pregnancy to make for a healthy litter"
The contibution to the health of the mother through being well fed/etc is not being accounted for which may garner benefits.

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.

"But then there's the argument about mass. While source material can be converted to denser material, it stands to reason that the amount of mass, or total weight of the converted material should not exceed that of the source unless additional material is being added during the conversion process."

Again the 'law' of conversion accounts for energy not being lost or, indeed, expended, and therefore adding mass to something even when this added particle does not have any weight but simply changes the structure, this is a possibillity in an open system, etc, etc (physics bores me). Certainly food intake + heat here would equal both a source of energy/additional source material. At the same time when we debated the possible role of water in the initial weight gain this seems now a very likely contributing factor considering the proven placental contributions.

At any rate there's definite evidence that a combination of both captital and income breeding both feature in the cycle as a whole.
I definitely agree that nutritional intake around the year is very important but still think it's just as important during pregnancy regardless of capital investment in the early stages.

[ConcinusMan]

I'm not sure the chicken example is a good one. Obviously those eggs are void of the mother once they are layed
Garter snakes are attached to the eggs. The blood that flows into these babies is carrying nutrients that the mother has consumed.

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.

It was my understanding that garter snakes are ovoviparous. If that's the case there is no placental connection after maturation of the ova or at least not after fertilization of the eggs. At least that's the definition I read:

"Ovoviviparous animals are similar to viviparous species in that there is internal fertilization and the young are born live, but differ in that there is no placental connection and the unborn young are nourished by egg yolk; the mother's body does provide gas exchange (respiration)"



I don't doubt that fluid and gasses, and perhaps water soluble nutrients to a limited extent, are contributed by the mother through the membrane even without a direct connection though. It was my understanding that once the ova are matured and fertilized, the young draw their nutrients by direct connection via blood vessels to the yolk, not the mother.

This is why we call them "Gravid", not "Pregnant";)


Well put, but with this - "Other than perhaps a little extra calcium, it doesn't take extra food mass or high nutrition during pregnancy to make for a healthy litter"
The contribution to the health of the mother through being well fed/etc is not being accounted for which may garner benefits.

I agree and I was thinking the same thing, but when I made that statement, I oversimplified it a bit. I didn't want to confuse the issue. Obviously if the mother is well nourished and in good health it will contribute to successful incubation and development of the young but the main source of nutrients for the developing young is the yolk, not the mother. The mother no longer has a direct vascular connection to that yolk. She finished doing that before fertilization didn't she? It was my understanding that the vascular connections from the mother to the egg is for gas exchange through the membrane.

[Mommy2many]

Could you remove the baby from the mother and nuture it within an artificial environment and produce viable young?

[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.:cool: 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.



:rolleyes: ^^ .... 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.