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Retic parthenogenesis

That was my first thought, then I saw
Genetic tests and molecular analyses revealed that all six baby snakes were produced by their mother alone—without any male genetic contribution.
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so I'm assuming they aren't making this great claim simply based on missexing the animal that cohabitates with her.
 
I remember when parthenogenesis seemed to me like such a miracle. Now we hear about a new case once or twice a year, it seems like. I wonder how often it happens out in the wild, with a much larger population.
 
I think it is interesting that parthenogenesis in boas and pythons has never produced a male offspring (to my knowledge). It should be able to if females are ZW and males are ZZ. They have produced offspring that are full clones of the mother (ZW) as well as WW females. But never ZZ...
 
DuxorW said:
I think it is interesting that parthenogenesis in boas and pythons has never produced a male offspring (to my knowledge). It should be able to if females are ZW and males are ZZ. They have produced offspring that are full clones of the mother (ZW) as well as WW females. But never ZZ...
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I didn't think they could...I guess I thought they were always full clones. But you're the geneticist!
 
There is a species (started out as a hybrid) of whiptail lizard in NM that is entirely female, all parthenogenesis...

Then there is a species of fish that I recently read about (also started out as a hybrid) that when they reach maturity the female has to breed with a male of the parent species to trigger her reproductive cycle, but does not utilize the sperm, instead she gives birth to clones of herself... It's insane what nature is capable of.
 
Nanci said:
I didn't think they could...I guess I thought they were always full clones. But you're the geneticist!
Click to expand...

Lol! Unfortunately genetics is so broad that I can't achieve genetic omniscience...yet!
It depends on how the diploid oocyte gets formed, there are a few different ways. My understanding is that there is only one case in boas/pythons that was confirmed to produce total clones of the mother. One boa constrictor gave birth to females that were not clones of the mother but were homozygous at all loci. Since they were female, if the mom was ZW then they would have to be WW, which was surprising because it was thought WW females wouldn't develop. Garter snakes have created viable males through parthenogenesis.

Something interesting about the sex chromosomes of boas/pythons is that they are homomorphic, meaning they look the same, unlike the ZW chromosomes of something like a corn snake, where you can easily distinguish the Z from the W even though they closer in size than the X and Y chromosomes of humans.

In fact, from what I've read and a discussion with a herpetologist, the sex chromosomes of boas/pythons are so homomorphic that they can't even be distinguished via karyotypes. Apparently there is an exception which is the dumerils boa, as there was a paper showing that their sex chromosomes can be distinguished by an inversion. But after reading the paper it looks like they took their samples from unsexed boas and assumed the boas that had one sex chromosome with an inversion and one sex chromosome without the inversion were from females. Because in snakes with heteromorphic chromosomes the female is always ZW, it seems like it has been assumed that female boas/pythons are ZW, which is a logical assumption. Boas and pythons definitely utilize the ZW system and not an XY system, because we know from genetic studies that the sex chromosomes of snakes are homologous to chromosome 6 of the butterfly lizard, whereas the X and Y have a different origin.

Anyway, where I'm going with this is a conspiracy theory that probably isn't true but is fun to pontificate on :)

What if in boas/pythons, females are ZZ and males are ZW? This is not outside the realm of plausibility evolutionarily, it just isn't the simplest explanation given what we know about other snakes with heteromorphic chromosomes. If those alleged WW females are really WW, if they grow up to be fertile they would only produce more females if females are ZW, since they would only be able to give a W to their offspring and the father would always contribute a Z, producing ZW daughters. But if females are ZZ and males are ZW, that would mean those WW female offspring are actually ZZ, and would be able to give birth to males and females, if they are fertile. I wonder if anyone is going to follow up on those daughters and see what they produce?
 
Reading about parthenogenesis in reptiles while I was in high school is what really got me fascinated with them. It just was the most amazing thing I had ever heard of at the time, it really made an impression. It seems nothing surprises me anymore when it comes to herps, or nature in general.
 
So it turns out that I might have been right, male pythons/boas may be the heterogametic sex. Thus, they are ZW (more appropriately XY, since that is the official designation when the male has two different sex chromosomes). If females are ZZ (really XX) this explains why parthenogens are always female in boas and pythons.

http://www.cnah.org/pdf/88512.pdf
 
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