Reptile & Amphibian Forums

On another forum a debate has arisen. SEveral of the questions have me wanting to verify some of the things I know, and also find out some of the things I don't know.

Someone there said that snakes have W and Z chromosomes instead of X and Y chromosomes like humans as their gender determining chromosomes. Does anyone know if the gender determining chromosomes in snakes have been officially named?

It was also mentioned that in snakes females have a WZ (two different gender-determining chromosomes) and that males have ZZ, which is exactly opposite of humans. Does anyone know if this is true and can you cite references if possible?

Another item for discussion is temperature-related sex-determination. Have there been any formal (or informal) studies to determine that temperature does NOT effect the genders of the babies? I would love to hear of any studies informal or formal that go to proving or disproving this.

Finally: Albinism. This question relates specifically to California Kingsnakes (though I'm sure that the answers for this question would relate to all kingsnakes, and perhaps all north american colubrids, if not all snakes everywhere)... Is it possible that albinism is a sex-linked trait in California Kingsnakes? Can anyone give me a logical argument using mendelian genetics (or any other way) that is clear and concise about why it COULD NOT be sex-linked? (or if they have an argument that is clear and concise as to how it could be sex-linked, I would love to hear about that too)

Thank you in advance for any responses to these questions and queries. the answers won't rock the planet off its axis, but they will help me to understand California Kingsnakes, Gender determination, and albinism better!

And for fun, a pic of one of my Cal Kings, who is supposed to be het for albino:

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~Sasheena

Those are all interesting questions, and I would also like to know the answers to those. Im not real clear on them, but I do know from biology that some animals do have differently named chromosomes and that females can have the two different chromosomes to become female. I think those types of animals are the ones that have a different name for them, so if snakes are WZ then the females would be WZ and the males ZZ. Ive heard a lot about temperature affecting the sex of the babies in reptiles, but Im not sure how it works or if it applies to snakes. Lastly, Ive never heard anything about sex-linked albinism, but Im not saying its not possible. If anyone else has more information, I would like to know about it too!

I don't know anything about snakes chromozones, BUT........

In snakes sex cannot and is not determined by incubation temps - period.

Albinism is a simple recessive gene that happens equally with males and females.

We are talking about large numbers here, not just someone's clutch(s). For example, someone can have a clutch of cal kings eggs (10) and 7 out of 10 can be all males; and all the albinos from another clutch could be all males, BUT......... temperature DID NOT CAUSE males or albinism. In the long run, it all rouds out to about 1:1 ratio on sex. If we all kept track of our clutches for a year and we had 1,000,000 babies hatch, roughly half would be males and half would females AND roughly half of ALL THE ALBINOS would be male and half would be females. That doesn't mean that someone could have a clutch of eggs that came out ALL THE SAME SEX, or someones albinos all happened to be male........... It does equal out in the long run.

Unfortunately there ARE IGNORANT breeders of snakes who still insist that incubation temps cause sex results SO SAD!

Kerby...

Do you have a website where i can see more pics of your snakes?

Travis

I haven't created a good website yet. I plan on making one as soon as I'm on summer vacation. Especially once all the babies start hatching out. Roll on 4th of July.... I have 48 eggs due to hatch that week, then a week or two later more hatchlings. So much fun!

In case you were interested in knowing exactly what I have:

2.4 Cal kings (11 eggs incubating, one snake ready to lay soon)
3.2 Florida Kings (all '03)
0.2 Apalachicola Kings (Blotched)... trying to get a male
0.0.1 Desert King (sold to us as an Eastern Chain)
0.1 Arizona Mountain King (seems to be gravid with three eggs)
0.1 Outer Banks King
1.3 Black Rat Snakes
2.5 Corns (and 36 eggs incubating)
1.0 Jurassic Milk
1.0 Rosy Boa
0.1 Jungle Carpet Python
1.4 Ball Pythons
0.0.1 Red Coachwhip (injured WC given to me by a student)
1.0 Egyptian Ratsnake
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~Sasheena

Hey there I may be able to help you with your blotched king problem. E-mail me at snakesunlimited1@aol.com and we can discuss it

>On another forum a debate has arisen. SEveral of the questions have me wanting to verify some of the things I know, and also find out some of the things I don't know.

>Someone there said that snakes have W and Z chromosomes instead of X and Y chromosomes like humans as their gender determining chromosomes. Does anyone know if the gender determining chromosomes in snakes have been officially named?

>It was also mentioned that in snakes females have a WZ (two different gender-determining chromosomes) and that males have ZZ, which is exactly opposite of humans. Does anyone know if this is true and can you cite references if possible?

I've seen snake gender chromosomes referred to as Z and W in several papers. I'd have to dig around a little to find some. The university library has an atlas of karyotypes (chromosomes) from a variety of species that includes some snakes. I can post that reference in a day or two.

The gender chromosomes in most birds are Z and W, and colubrid snakes follow the same pattern. Boid snakes do not seem to have sex-determining chromosomes of different sizes. I don't know about other families of snakes.

>Another item for discussion is temperature-related sex-determination. Have there been any formal (or informal) studies to determine that temperature does NOT effect the genders of the babies? I would love to hear of any studies informal or formal that go to proving or disproving this.

I know of one formal study where northern pine snakes were incubated at a variety of temperatures, but I don't think the sexes of the babies were recorded. Have to hunt that up.

>Finally: Albinism. This question relates specifically to California Kingsnakes (though I'm sure that the answers for this question would relate to all kingsnakes, and perhaps all north american colubrids, if not all snakes everywhere)... Is it possible that albinism is a sex-linked trait in California Kingsnakes? Can anyone give me a logical argument using mendelian genetics (or any other way) that is clear and concise about why it COULD NOT be sex-linked? (or if they have an argument that is clear and concise as to how it could be sex-linked, I would love to hear about that too)

I have never bred California kings, so I can't give you a positive answer. But here is an argument for why amelanistic is not sexlinked in corn snakes. You can use the same reasoning for kings:

1) The Z (or mammallian X) chromosome is much longer than the W (or mammalian Y) chromosome. Generally a sexlinked locus refers to a locus on the Z (or X) chromosome that is not paired in the W (or Y) chromosome.

2) A female MUST show the effect of a mutant gene that is sexlinked in her single Z chromosome.

3) A male shows the effect of a mutant gene if the mutant is recessive to the normal allele and is homozygous for the mutant allele. This is true for both sexlinked and autosomal loci in males. As amelanistic corns can be produced by mating two normally colored snakes, amelanistic must be a recessive mutant gene.

4) Theoretical results of crosses if amelanistic is a recessive mutant. Symbols--W = female chromosome, a = amelanistic on Z chromosome, A = normal allele on Z chromosome.

Male homozygous amelanistic (aa) x female normal (AW) -->
1/2 Aa = male normal (heterozygous for amelanistic)
1/2 aW = female amelanistic

ALL the amelanistics from this cross MUST be female.

5) Actual results of a male amelanistic corn x a female normal corn: all babies, both male and female, are normal. (Source: Bern Bechtel's original cross of an amelanistic male corn x female normal corn. Same results in a mating of my corn snakes.) Therefore, the amelanistic locus in corns is not sexlinked.

If the same results come from a Cal king mating, then you can rule out sexlinkage.

Paul Hollander