# Importance of egg pole position for a developing egg



## dysphoria (Apr 1, 2012)

I was recently having a discussion with a fellow frogger about caring for tinc eggs, and the subject of egg poles(or hemispheres) came up. There was some discussion regarding the vegetal pole(the lighter side) being out of position(towards the top) that may slow, or even prevent an egg from developing. I've seen some evidence of this myself with various vent clutches having some eggs that slid or turned for whatever reason - and those ones tended to not develop. I never made the connection until now, and was wondering if anyone could expand on why egg position has a bearing on development. 

Does this have something to do with one side of the egg being more permeable? Does the oviducal jelly suffocate the mispositioned egg? Perhaps gravity has some influence in development? - this seems odd considering that I've seen vents lay eggs upside down in film containers that developed without issue. Anybody have some reading they can point me at? I've been scouring the web for a way to corroborate this, but all the stuff I can find is geared towards general frog embryology and doesn't cover what I looking for. Anybody?


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## hypnoticaquatic (Dec 19, 2012)

id guess is not one thing but a complex situation, i remember watching some info on developing eggs in space, this looked like one of the things i had seen NASA - Avian Development Facility - Skeletal Development in Embryonic Quail its on bird eggs but still would relate to the development of anylife in general after all they were doing this to see how our eggs would develop in space but were not going to do that type of r/d on ourselfs to start.

im sure there is some relation to the egg not developing due to being moved just like reptile eggs i think they drown in there own fluid from what i remember been years from last time i thought/looked into it.


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## Ed (Sep 19, 2004)

hypnoticaquatic said:


> im sure there is some relation to the egg not developing due to being moved just like reptile eggs i think they drown in there own fluid from what i remember been years from last time i thought/looked into it.


Actually reptile eggs unlike avian eggs form an attachment to the shell which causes changes in the shell to allow for greater gas exchange (O2, CO2)...rotating the egg in early stages of development can tear the embryo away from the shell resulting in it's death.. For it to drown, it would have to have lungs functioning and breathing air and have that air replaced by some liquid... this is not possible during the period where the egg is at risk... There is a good statement with references in Koler, Gunther; Haecky, Valerie; 2005; Incubation of Reptile Eggs: Basics, Guidelines, Experiences; Krieger Press..specifically 


> The attachment of the reptile embryo marks an important step in the development, since this leads to a drying of the eggshell directly above the embryo. This increases the gas permeability of the eggshell and protects the embryo from lack of oxygen (Thompson, 1985; Whitehead, 1987). If the reptile egg is turned upside down, the embryo ends up underneath the yolk and is trapped there because of its adhesion to the inner shell membrane. The large bulk of the yolk on the embryo prevents normal development and can lead to deformities or death (Eweart, 1985; Ferguson, 1985).


This attachment doesn't form in amphibian eggs... and due to the difference in the density of the yolk and the embryo, gravity orients the egg into the correct position... Pre-fertilization you can impact the egg by centrifuging the eggs (but that is going to be a significantly greater amount of motion than messing with them....) which can result in deformation of the embryos (specifically microcephaly)... Simple disturbance even enough to change the rotation shouldn't impact the development since gravity is going to correctly reorient the eggs.. See for example Current Topics Developmental Biology; Volume 11; 1977; Academic Press). (and when a male waters the eggs, it can involve some significant effort (see anecdotal reports of "males smashing eggs"..)... I would suspect observer bias to be part of the perception... 

Some comments 

Ed


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## hypnoticaquatic (Dec 19, 2012)

well the first part on drowning can happen even without having lungs filled up with water, think of it the same way a fish can drown just a lack of 0² from the water so if the egg tore away from the shell where it was getting its o2 from it essentually drowns/suffocates really just splitting hairs imo. 

thanks for clarifying up the difference between the two its always nice learning why things work and why.


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## Ed (Sep 19, 2004)

hypnoticaquatic said:


> well the first part on drowning can happen even without having lungs filled up with water, think of it the same way a fish can drown just a lack of 0² from the water so if the egg tore away from the shell where it was getting its o2 from it essentually drowns/suffocates really just splitting hairs imo.
> 
> thanks for clarifying up the difference between the two its always nice learning why things work and why.


The tearing of the major blood vessels in the region of the shell attachment would be more likely to cause death...since they are there for gas exchange.... 

Ed


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## Ed (Sep 19, 2004)

Just to be anal for a moment.. 
Drowning is the process of experiencing respiratory impairment from submersion/immersion in liquid... 

The fish isn't suffering from respiratory impairment from the submersion..instead it is being deprived of dissolved oxygen.... 

Some comments 

Ed


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## papafrogger (Oct 21, 2012)

Ed said:


> Actually reptile eggs unlike avian eggs form an attachment to the shell which causes changes in the shell to allow for greater gas exchange (O2, CO2)...rotating the egg in early stages of development can tear the embryo away from the shell resulting in it's death.. For it to drown, it would have to have lungs functioning and breathing air and have that air replaced by some liquid... this is not possible during the period where the egg is at risk... There is a good statement with references in Koler, Gunther; Haecky, Valerie; 2005; Incubation of Reptile Eggs: Basics, Guidelines, Experiences; Krieger Press..specifically
> 
> 
> This attachment doesn't form in amphibian eggs... and due to the difference in the density of the yolk and the embryo, gravity orients the egg into the correct position... Pre-fertilization you can impact the egg by centrifuging the eggs (but that is going to be a significantly greater amount of motion than messing with them....) which can result in deformation of the embryos (specifically microcephaly)... Simple disturbance even enough to change the rotation shouldn't impact the development since gravity is going to correctly reorient the eggs.. See for example Current Topics Developmental Biology; Volume 11; 1977; Academic Press). (and when a male waters the eggs, it can involve some significant effort (see anecdotal reports of "males smashing eggs"..)... I would suspect observer bias to be part of the perception...
> ...


Could you clarify this a little bit? Sounds to me you are saying that disturbing the pole position will not effect development due to gravity re-orienting the egg. If thats the case then why do people lose eggs due to them flipping over? Im not doubting your answer just trying to understand.


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## Reef_Haven (Jan 19, 2011)

My understanding is, eggs that do not re-orient themselves were either infertile to begin with or have stopped developing for some other reason.

http://www.dendroboard.com/forum/breeding-eggs-tadpoles/88782-need-some-help-terribilis-eggs.html#post784947


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## papafrogger (Oct 21, 2012)

Reef_Haven said:


> My understanding is, eggs that do not re-orient themselves were either infertile to begin with or have stopped developing for some other reason.
> 
> http://www.dendroboard.com/forum/breeding-eggs-tadpoles/88782-need-some-help-terribilis-eggs.html#post784947


Thanks that cleared it up alot.

So pole position is essentially NOT important? As long as the egg is fertile and developing we could manipulate egg position (within reason) and they will reorient themselves? Thats pretty cool if you ask me.

Edit: To rephrase, not that pole position is unimportant; but something we shouldnt be concerned with?


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## Judy S (Aug 29, 2010)

ED...so why is it that chickens shuffle the eggs around daily? 

ctually reptile eggs unlike avian eggs form an attachment to the shell which causes changes in the shell to allow for greater gas exchange (O2, CO2)...rotating the egg in early stages of development can tear the embryo away from the shell resulting in it's death.. For it to drown, it would have to have lungs functioning and breathing air and have that air replaced by some liquid... this is not possible during the period where the egg is at risk. 

This may occur several times during the day...and there is an attachment to the shell itself...just askin'


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## Ed (Sep 19, 2004)

Judy S said:


> ED...so why is it that chickens shuffle the eggs around daily?
> 
> This may occur several times during the day...and there is an attachment to the shell itself...just askin'


In the most simplistic reason, to prevent adhesions but this is apparently an oversimplified reason.. One of the things on my reading list (which is oddly fairly long .... ) is this 19 - Reasons for the dichotomy in egg turning in birds and reptiles - University Publishing Online 

Ed


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## Judy S (Aug 29, 2010)

Since birds and reptiles/amphibians are related somewhat in the evolutionary chain...interesting that the egg/no egg turning changed along the way as well. Thanks, Ed, for edifying a complicated issue....do you just remember this stuff and the places to find the information, or do you have physical cross-references to find "stuff" quickly???


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## Ed (Sep 19, 2004)

Judy S said:


> Since birds and reptiles/amphibians are related somewhat in the evolutionary chain...interesting that the egg/no egg turning changed along the way as well. Thanks, Ed, for edifying a complicated issue....do you just remember this stuff and the places to find the information, or do you have physical cross-references to find "stuff" quickly???


I generally have read it and remember it (or at worst have a good idea of the topic and can track it down via a quick search). 

Ed


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## Judy S (Aug 29, 2010)

amazing...


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## Ed (Sep 19, 2004)

Judy S said:


> amazing...


Not really, think of it this way... how many people can cite sports statistics/player/year in thier favorite sport (or other topic (say music))? It's the same, just a different subject matter. 

Ed


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## Judy S (Aug 29, 2010)

I'm sort of convinced, having three brothers, that it is mostly a man thing...women think more globaly..too many things at one time to concentrate on for something like E.R.A.'s... gotta remember the dirty socks, T.P., milk, etc. Mars/Venus...


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