Thursday, May 9, 2013

Sex determination in Reptiles

Figure 17.20. Temperature-dependent sex determination in three reptile species: the American alligator (Alligator mississippiensis), the red-eared slider turtle (Trachemys scripta elegans), and the alligator snapping turtle (Macroclemys temminckii).
This picture was taken from this site
Did you know, not all animal's sex is determined by sex chromosomes? Reptiles are a classic example of this. Some reptile’s sex is determined by temperature.  As you can see from the picture on the right, if a Alligators nest falls below 31 degrees Celsius all of her babies will be female but if she keeps her nest at about 32 degrees she will have all males. At about 31.8 degrees Celsius there is a mix of both male and females. This site explains this in more detail, but the general idea is that there is a enzyme named aromatase and this is used to turn testosterone (the male hormone) into estrogen (the female hormone). It is thought that 29 degrees to about 31 degrees Celsius aromatase is very active getting rid of all that pesky testosterone and making lots of estrogen and thus female babies. 
As cool as this system is not the way it works for all reptiles-- this doesn’t apply to snakes nor is it true for all turtles.

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