INCUBATING FOR FEMALES

Carol S

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At what time during the incubation period is the sex of the developing tortoise created?
 

turtlesteve

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Sometime in the middle of the incubation period. I have a research article on this I pulled a couple years back, I’ll see if I can find it later.
 

turtlesteve

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OK, I found the article I was looking for. In red-eared sliders, the peak (most sensitive time) for TSD occurs when the embryo is about 1.3 cm in total length. This is more or less the 2nd trimester and occurs when the carapace is fully formed. It's not clear when the temperature-sensitive period starts. Reference is:

Temperature-Dependent Sex Determination in
Reptiles: Proximate Mechanisms, Ultimate
Outcomes, and Practical Applications

Crews et. al.

Lots of extremely interesting information in this article. In many cases, artificial incubation methods that reliably produce females will also produce split scutes. I suspect that this occurs because the temperature is being held constant, and because it's too high, too early in the incubation period. I believe it's advantageous to hold eggs in the mid-80s until the TSD period starts, and then only elevate them to promote TSD at that time. This obviously requires that you are able to track the embryo size during development.
 

Tom

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OK, I found the article I was looking for. In red-eared sliders, the peak (most sensitive time) for TSD occurs when the embryo is about 1.3 cm in total length. This is more or less the 2nd trimester and occurs when the carapace is fully formed. It's not clear when the temperature-sensitive period starts. Reference is:

Temperature-Dependent Sex Determination in
Reptiles: Proximate Mechanisms, Ultimate
Outcomes, and Practical Applications

Crews et. al.

Lots of extremely interesting information in this article. In many cases, artificial incubation methods that reliably produce females will also produce split scutes. I suspect that this occurs because the temperature is being held constant, and because it's too high, too early in the incubation period. I believe it's advantageous to hold eggs in the mid-80s until the TSD period starts, and then only elevate them to promote TSD at that time. This obviously requires that you are able to track the embryo size during development.
It would be great to get time frames for this. Candling is not an exact science...
 

turtlesteve

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It would be great to get time frames for this. Candling is not an exact science...
The reason I didn’t go with time is that the rate of development varies by species and temperature. I am inferring peak sensitivity is about ~6.5-7 weeks prior to hatching for red ears at 27C. The window for TSD, centered on this time, is only 2-4 weeks long.

Edit: to prove my point, just pulled a paper for painted turtles (because it was not behind a paywall) and it looks like the equivalent development stage is only about 4 weeks prior to hatching, because painted turtles hatch at an earlier developmental stage.
 
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method89

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This is a bit of a hijacking so I apologize in advance but where are you finding the articles and/or papers. I search and search and all I ever find are fluff on turtles and tortoises. I'm looking to learn as much as I can and I don't feel like I'm getting anywhere other than the things I learn here. Thanks.
 

turtlesteve

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This is a bit of a hijacking so I apologize in advance but where are you finding the articles and/or papers. I search and search and all I ever find are fluff on turtles and tortoises. I'm looking to learn as much as I can and I don't feel like I'm getting anywhere other than the things I learn here. Thanks.
From scientific journals. Some papers ( the minority unfortunately) are free access. When I get some time later I will make a new thread to avoid derailing this one.
 

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