What is the relationship btwn incubation temperatures and the sex of hatchlings? I read a long time ago that the sex of baby turtles, alligators and other reptiles is determined by the temperature the eggs are kept. so how does this relate to Colubrids? has any research been done on this... the reason i ask is because of the sex ratios we see in Kings and Milks... some may produce an entire clutch of females or males, or high male low female or hi female low male while others have an even distribution so why is that??

Exert i just found:
Although the exact mechanism by which temperature determines sex is not
known, it appears that temperature determines whether the embryo develops
testes (becomes male) or ovaries (female). Early embryos have indifferent
gonads capable of becoming either testes or overies. In many turtle
species, higher incubation temperatures turn the early gonads into ovaries,
resulting in females, while lower temperatures turn the gonad into testes,
resulting in males. The reverse is true in alligators, where higher
temperatures yield males and lower, females. In mammals, the same process
occurs, but is regulated by genes rather than temperature: a particular
gene called the testis determination factor on the Y chromosome transforms
the early gonads into testes in males. Females, with 2 X chromosomes,
don't have the gene so ovaries develop.


One way in which temperature might affect the development of the gonad is
by regulating steroid hormone production. For instance, if turtle eggs are
incubated at high, female-producing temperatures but treated with the male
steroid testosterone, males will develop. Or, if eggs at low,
male-producing temperatures are treated with the female steroid hormone
estrogen, females develop instead. All steroid hormones are synthesized
from the cholesterol molecule, and share common features in their synthetic
pathway. Testosterone can be converted to estrogen by the enzyme
aromatase, for instance. So it is possible that in reptiles, certain
enzymes involved in the synthesis of estrogen and testosterone are
temperature-sensitive.

Louise Freeman

Mary Baldwin College



Source: An Introduction to Behavioral Endocrinology, by R. J. Nelson
(2000) pp. 122-124





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Thanx
Royal Blue Reptilez

~ZF

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