Diapause in tortoises

[EJ]

This term drives me nuts. Some believe it is a necessity for some species. In other words... the eggs will not hatch unless there is a diapause.

All species seem to be capable of going through a diapause. Does this mean we have to subject all tortoise eggs to a diapause?

A diapause is triggered for one reason or another and needs to be triggered again to continue developing.

What if it is not triggered in the first place... it then does not need to be triggered again.

Then there is the trigger... it is probably either temperature or humidity or both. How does one know what that trigger is?

The point of this rant is that diapause in tortoise eggs is not a necessity. This is a similar line of thought as hibernation. In fact... it is the same line of thought as hibernation.

If the incubation conditions are correct for proper development to begin with the egg will develope normally.

Eggs laid early in the season most likely do not go through a diapause(tough to confirm). Eggs laid latter most likely do(easy to confirm).

The first I heard of this, and I believe when the term came into vogue, is with the first Egyptian tortoise eggs in captivity. Many believed they needed to go through a diapause in order to hatch... proven not true.

You get a limited chance to hatch an egg. The more you stress that egg the chance of it hatching most likely decreases.

[Catwoman63]

Can you please explain what a "diapause" is for us that do not know this term? thank you x

[EJ]

A diapause is when the development of a tortoise egg is arrested or stops developing. It is thought that this is a survival mechanism to allow the egg to hatch in more favorable conditions.

If eggs that were laid during the end of a normal season hatched during the off season (dry, cold) the hatchlings probably wouldn't be able to hatch or die in the process. With a pause in the development the egg is allowed to hatch under more favorable conditions.

An important point is that when the eggs are laid in a period that allows full development... a diapause does not take place.

Originally Posted by Catwoman63

Can you please explain what a "diapause" is for us that do not know this term? thank you x

[Catwoman63]

Thanks Ed i understand it now x

[Kirkie]

Theres a paragraph half way diwn this that suggests that the pre oviposion temperatures the female expirience may influence whether an egg enters diapause.

http://rspb.royalsocietypublishing.o...2012.0100.full

I've got another Dawn Wilson study here on K. Baurii diapause. If I remember correctly they started eggs from the same clutch *at a lowish incubation temperature. If they showed no development after 3 weeks they were diapaused and later returned to higher temps and hatched as did those that started immediate development at a lower temp.

I've currently got some Baurii eggs that started and stopped stored away at a low temperature. Their clutch mates are due in a few weeks, I should know late July if the temp drop worked for the other or if they just died early on.

[EJ]

You're welcome. When it caught on in the chelonian world... which wasn't all that long ago... everybody went nuts on the idea. Now every tortoise needs to be forced into a diapause to develope. Don't get me wrong... there are a small number of species eggs that do seem to benefit from a diapause but I think it has more to do with not understanding the tortoise natural biology than a necessity.

Originally Posted by Catwoman63

Thanks Ed i understand it now x

[EJ]

I believe diapause has been pretty well documented in aquatic chelonians but I think it is a relatively new concept in tortoises. One of the most compelling bit of evidence that it is beneficial in some species of tortoises is in the case of the Flattail tortoise. Outside of that I wonder if it is as necessary in other species as some make it out to be.

How does that compare to those eggs that were incubated at a normal incubation temperature? That's my point. If the eggs are deposited in an environment that supports proper development for the species they would probably develop normally. There has to be a trigger at both ends.

When did you determine that development stopped in the eggs you are incubating. How do you know it was temperature and not humidity that caused any arrest if there was one.

Finally... can you send me a copy of the second paper... please.

Originally Posted by Kirkie

Theres a paragraph half way diwn this that suggests that the pre oviposion temperatures the female expirience may influence whether an egg enters diapause.

http://rspb.royalsocietypublishing.o...2012.0100.full

I've got another Dawn Wilson study here on K. Baurii diapause. If I remember correctly they started eggs from the same clutch *at a lowish incubation temperature. If they showed no development after 3 weeks they were diapaused and later returned to higher temps and hatched as did those that started immediate development at a lower temp.

I've currently got some Baurii eggs that started and stopped stored away at a low temperature. Their clutch mates are due in a few weeks, I should know late July if the temp drop worked for the other or if they just died early on.

[Baoh]

Ed, folks have claimed such for spider tortoises, which I have no reason to dispute (I have never kept them), but folks have also claimed such regarding South African leopard tortoises, which I am not sure why that would be the case. Your thoughts on either type are more than welcome.

[EJ]

I had one egg from a Spider tortoise. It was not subjected to a diapause and it hatched but that is only one egg. I do think that is still good enough evidence for that species.

It is interesting that there is compelling evidence that it increases the success rate for Flattail tortoises but that could be due to the fact that keepers aren't getting it right in the first place.

The San Diego zoo has been hatching out SA Leopards for many years and I can't seem to remember a mention of a diapause. I do remember a recent note by a Richard Fife that it increased his success in hatching out the race. He lives in Arizona.

Keep in mind that a diapause seems to be caused and broken by temperature, humidity or both

Again... I believe it is not a necessity but an adaptation.

Originally Posted by Baoh

Ed, folks have claimed such for spider tortoises, which I have no reason to dispute (I have never kept them), but folks have also claimed such regarding South African leopard tortoises, which I am not sure why that would be the case. Your thoughts on either type are more than welcome.

[Helen M]

Aw Ed. I was seriously hoping one of my horsfield eggs had gone into diapause but more than likely it has died. Oh well.

Anyway I too think it strange that keeping animals in optimum environments will lead to an inefficient use of time and resources. Animals are hardwired to survive and proliferate when times are good. So unless there's something more complex going on then there's no reason for diapause to be necessary to hatch eggs..

Helen x