 | market - home |
|
| market - home |
|
 |
 |
News & Events:
|
Posted by Dr. Phil on April 09, 2002 at 22:18:50:
In Reply to: eggs posted by Thane on April 09, 2002 at 12:08:53:
It's my humble opinion that snakes, just as most other reptiles' (I suspect maybe all of them) sex is thermally determined during the early stages of embryonic development. The statistical evidence is strong in most groups of reptiles, and is very precisely determined in most crocodilians, many chelonians, and at least a few saurians (think loepoard geckos, for one). So the question is, why would ophidians be any different, when these other little-related groups are so ruled by this law of nature?
I strongly suspect that the reason it's not as obviously clear cut in snakes compared to classic cases such as any crocodilian or turtle species is probably because the interval of incubation temp where you obtain roughly even sex ratios is probably much wider than in those other groups, so it's then possible to avoid any extremes in ratios as long as one avoids incubating at either of the opposite ends of the incubation thermal spectrum. It also might just be in some species that the temp extremes where the sex ratio would start getting very lopsided also happen to be very near the same temperature zone that is lethal do developping embryonic tissue. Spinal kinking is typical of this zone in many species of snakes, not just indigos, and (as Fred seems to have noticed with his own animals), males are usually produced at the higher temp range and females at the opposite, cooler end.
This is of course (yet another) theory of mine, relying mostly on anecdotal evidence. But who within this circle of breeders has never himself experienced or witnessed a fellow breeder hatch out a large batch of eggs from a given species and been comfronted with a sex ratio so uneven that it seamingly defies all odds? In such instances I would tend to think that the eggs were somehow exposed to at least temporary thermal extremes during the early stages of incubation (or even a few days before being laid, as embryonic development starts well before the laying itself, of course).
Just another opinion...
Dr. Phil
PS: So I hereby extend my neck and boldly predict that the cooler incubated batch of Dean's will hatch a "better" ratio (females>males) than the one incubated at 78-80F, given that both clutches were incubated at each their selected temp range right from the start, of course!
