If you have the time, check out the great exhibit at the Museum of Science – “Geckos – Tails to Toepads”. They have over 60 geckos on display from a wide variety of species, and the terrariums they have them in are beautiful. I know they gave me some ideas for how to make a terrific display! The kids will love it.
In Leopard Geckos the sex of the babies is determined by the temperature the eggs are incubated at. This is called temperature dependent sex determination (TSD). TSD occurs in some other lizards, most turtles and all crocodilians. For all other vertebrates sex is determined by chromosomes, with either an X or Y (XX=female, XY=male) or a Z and W (ZZ=male, ZY=female) determining the sex of the offspring. Their may, in fact, be sex chromosomes in the animals with TSD, but they may be very tiny chromosomes, as many reptiles have “mini-chromosomes” only, or in addition to the larger, more typically sized chromosomes of other vertebrates. The sex determining genes may be expressed in a temperature sensitive way, but this is only a possibility (hypothesis) right now.