Reptile & Amphibian Forums

I've noticed lately that several people with jungle corns available are male heavy. When I say jungle corns in this case, I'm referring specifically to cal king x corn hybrids. I was starting to wonder if it was just a coincidence, but I met someone at a herp show this weekend with several available. His were actually 75% corn, 25% jungle (jungle bred back to a corn) and he had quite a few males for sale but no females. After I asked him about them, he said he did hatch 2 females, but was holding them both back. He did say he tends to get a lot more males than females from his pair though.

I was wondering what you guys think of this? Do those of you who've bred jungles agree that they tend to produce mostly males? I'd be interested in hearing what the sex ratio was in other breeders' jungle clutches whether they were male heavy or not. I know when crested gecko x R. chahoua hybrids are made, they all end up male so I thought it was interesting that another type of hybrid might produce predominantly males. If any of you are more familiar with genetics than I am and can explain (or speculate on) this phenomenon I'd be interested to hear your thoughts. Thanks.

i bet they are just holding back more females which make it seem like a bigger ratio
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jake barney
1.1 ball pythons
0.2 corns
1.0 cal king
0.0.1 wc garter
1.o cb son

>I was wondering what you guys think of this? Do those of you
>who've bred jungles agree that they tend to produce mostly
>males?

Snakes are like birds in their sex chromosomes. That is, chromosomally, males are ZZ and females are ZW. Since half the unfertilized eggs are expected to carry the Z chromosome and the other half should carry the W chromosome, fertilization with Z bearing sperm should produce ZZ (male) and ZW (female) embryos in equal ratio. Heterogametic (ZW) lethality due to a "Haldane's Rule" effect, might be possible but my impression is that Haldane's Rule effects are all or nothing, i.e. all dead female embryos or no dead female embryos. There might be an incipient effect but breeders would need to keep careful records - including percentage of unhatched eggs in clutches producing mostly male live hatches.

One thing I have noticed in cornsnake X bullsnake crosses is that hybrid females may produce eggs 3 or 4 times normal size that mostly don't hatch. Some don't even have eggshells. This may be an incipient Haldane's Rule effect but I have not made enough crosses to know with any certainty.

>I know when crested gecko x R. chahoua hybrids are made, they all end up male...

This also happens in certain crosses of froglike amphibians. Unlike snakes (but like most amphibians), lizards do not have cytologically distinquishable sex chromosomes. Sex inheritance is in some way genetically determined but I doubt the mode of inheritance has been worked out. It could be something similar to platyfish where females from one river in Mexico will produce all males when crossed with males from certain other Mexican rivers.

The chromosome difference between snakes and lizards is interesting because it supports the hypothesis that snakes are modified plesiosaurs (extinct aquatic reptiles) instead of modified burrowing lizards as commonly supposed.

Bigfoot

Very interesting stuff. Unfortunately I'm not nearly as familiar with genetics as you seem to be, but I understand a lot of what you're saying and it makes sense.