Multiple fathers.

I'm not sure if this something that has been covered but if a male tortoise has successfully fertilised a females eggs and produced offspring, the female can produce fertile eggs for years without seeing that male again. So if a second male was to mate with the same female, would the offspring be his or still the first males? Or even a bit of both?

I've wondered that myself and don't remember if it's been touched on or not. @tortadise @Tom @Yvonne G @DeanS @Gerards will be interesting to see the opinions.

Not an opinion but rather a question regarding their biology. This is an interesting question. I would assume a mixture of both…? Being that they can accept sperm from multiple males to fertilize their eggs to begin with, I don't see a reason that this advantageous adaption should not continue through the years….Especially considering that over several years the animals may disperse to different locations, thus carrying another male's progeny with them…?

I would have thought that it could be a combination of both. But then I read this book and it makes me wonder. It talks about how some organisms, mostly insects I think, have the ability to choose which sperm they use. And that the mail can also have an influence. I haven't read the whole book yet but it is interesting.

In the book they did mention how tortoises can store sperm but I'm not sure if they say anything else about tortoises. I'll let you know when I'm done reading it.

It would be a mixture. What percentage I can't answer that. It's a pool per say when the oviduct begins developing and the sperm attaches to the follicles and eggs begin to develope it could be from any of the males that inseminated the female. Bit different than humans where there's just one little swimmer that causes the egg to develop.

An interesting note in populTion and genetic diversity is to have multiple males breed a female or two to dilute it a bit and keep things a bit more variant in terms of lineages. Of course those are still considered let's say bloodline "A"

I agree it would be a combination.

Also, different species store sperm for different periods of time. I've heard multiple cases of leopards storing it for five years, but sulcatas seems to only be able to store it for a few months. Jerry Fife did a presentation on this at the TTPG and I saw something similar in my own herd.

Turtlepete said:

Not an opinion but rather a question regarding their biology. This is an interesting question. I would assume a mixture of both…? Being that they can accept sperm from multiple males to fertilize their eggs to begin with, I don't see a reason that this advantageous adaption should not continue through the years….Especially considering that over several years the animals may disperse to different locations, thus carrying another male's progeny with them…?

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You are wise beyond your years. Have you lied to us about your age on your profile?

tortadise said:

It would be a mixture. What percentage I can't answer that. It's a pool per say when the oviduct begins developing and the sperm attaches to the follicles and eggs begin to develope it could be from any of the males that inseminated the female. Bit different than humans where there's just one little swimmer that causes the egg to develop.

An interesting note in populTion and genetic diversity is to have multiple males breed a female or two to dilute it a bit and keep things a bit more variant in terms of lineages. Of course those are still considered let's say bloodline "A"

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Kelly, out of curiosity (though I don't necessarily expect there to be a definitive answer on this), does the age of the sperm affect the viability of the egg resulting from it, or it's chances of developing into an egg to begin with?

@Tom, I wonder how this phenomenon is studied….And has it been studied in other species? Redfoots, for example?

The only way to really test it is to test the adults and offspring. Not certain about the internal stuff. That would be a question for a geneiologist or micro zoologist or something. I'd think the procedure getting to the oviduct to sample would end up being a very tricky surgery to put one under for that kinda information. Is speculate it's possible to assess which animal and what percentage relates either sire/damn. I know the most extensive studies have been on the Galapagos. But most of that was phylogeographic and relation to which island or subspecies the animals were. Not sure if they can code search for mother or father(s).

So all that blabbing above to short answer. I dunno. Lol

Turtlepete said:

Kelly, out of curiosity (though I don't necessarily expect there to be a definitive answer on this), does the age of the sperm affect the viability of the egg resulting from it, or it's chances of developing into an egg to begin with?

@Tom, I wonder how this phenomenon is studied….And has it been studied in other species? Redfoots, for example?

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way

All biological material will degrade over time. There is no mechanism in place to repair sperm within any known creature. It is simply replaced with new sperm.

I'd imagine this degradation does play a part in egg fertilization and genetic issues we sometimes see popping up, even within short periods of time.

Turtlepete said:

@Tom, I wonder how this phenomenon is studied….And has it been studied in other species? Redfoots, for example?

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I know of no "official" studies on this subject, just lots of anecdotal evidence from individuals and their tortoises.

The leopard tortoises I referenced above had contact with a male and produced annual viable clutches. Upon removal of the male, they continued producing fertile eggs for 5 years.

Jerry Fife's example demonstrated that his female had been accidentally bred by a male and her fertility (measured by hatch percentage) dropped off with each successive clutch, until it reached a 0% hatch rate. Re-introduction to a male resulted in high percentage hatch rates.

I had something similar in my adult sulcata enclosure with consistent high hatch rates out of each of my females. After the male injured his penis and was removed from the female enclosure hatch rates dropped off significantly with each clutch until it reached zero by the end of the laying season that year. Introduction of a new male resulted in high hatch rates for the entire next laying season and each year after.

Turtlepete said:

Not an opinion but rather a question regarding their biology. This is an interesting question. I would assume a mixture of both…? Being that they can accept sperm from multiple males to fertilize their eggs to begin with, I don't see a reason that this advantageous adaption should not continue through the years….Especially considering that over several years the animals may disperse to different locations, thus carrying another male's progeny with them…?

Click to expand...

No chelonian is known to have what biologists call sperm competition (many snakes do). It might occur, but I have not ever seen it reported in any literature. On the other hand multiple paternity has been observed in a few species, so not to big of a stretch to consider it may be widespread within chelonians. Fertilized ova are retained, not sperm, at least as far as I recall from reading published account by people who investigate these things. The fertilized ova descend in the egg making canal based on hormone feedback from body condition and the environment. I don't recall reading what becomes of the fertilized ova over much longer periods of time such that they lose being able to become eggs with neonates.

These are very interesting questions (to know more about these kinds of reproductive strategies) that are usually answered by academics. Industry (applied science) doesn't care much to pursue these kinds of basic research. I always figured entities like the TSA should support more basic research. I think they have a hard time fundraising for these kinds of studies. Some larger zoos do this kind of work too. I played around with some of these things while in grad school, but they can be a conflict when 'good grades' are more important and teachers have limited resources.

To that end I have some basic research on why that one Australian sideneck can lay their eggs under water. More interesting to me is the behaviour to do it. How do they "know" they can? Blah blah.

Thank you @Will. That is the most I've heard on this subject.

So applied to my anecdotal observations, those leopard females were hanging on to fertilized ova for 5 years? And sulcatas seem to only be able to hold on to them for a few months? My sulcatas kept laying eggs, but the fertility percentage dropped off sharply with each successive clutch.

Because non fertilized ova dropped down into the space.

Awesome. Thanks for the information @Will, very interesting. The Australian Sideneck thing is an especially interesting question as well which I'd love to hear more on.

Very interesting thread.
Thanks all.