Sex-determination in Collared Lizards

Sex determination in reptiles has generally been considered to come in two forms: genetic or temperature dependent. However, recent studies have show that in some reptiles, like Bassiana duperreyi, this is not always the case. Even the three types of temperature sex-determination do not explain all forms of sex-determination now, as there are cases where temperatures override the genetic sex. The authors of the article performed test on collared lizards to determine if incubation temperatures changed the genetic sex of the hatchlings. The authors collected female collared lizards from the wild that were already impregnated and moved them into research chambers at Oklahoma State University. Next, the authors waited for the females to lay eggs and then collected the eggs once laid. The eggs were the placed in vials one of seven incubators set at a constant temperature between 21 and 35͒℃. Eggs remained in the incubators until hatched and the sex of the hatchlings were determined. Although each incubator had a sex ratio of approximately 1:1, the data showed a significant sex-bias in the temperature ranges of 27-32℃ and 32-35℃. Female hatchlings increased in the first range and decreased in the second. The sex-determination fell into a TSD II pattern, but was male-female-male instead of the typical female-male-female pattern. Theses results add to the information that sex-determination in reptiles does not fall into the prescribed categories as scientists once believed. The article mentions that sex-determination in less than 10% of all reptile species had been determined. Knowing which species fall into the TSD and GSD overruled by temperature categories is valuable information. As global climate change continues to effect overall temperatures, understanding the sex-determination of reptiles will help identify which species are most at risk for becoming too heavily dominated in one of the sexes. Having too many of one sex and not enough of the other diminishes the chances for successful reproduction, which will in turn cause a decline in the reptile species and possibly in the reptile population as a whole.


 
Images: Left-adult male collared lizard, Right: collared lizard hatchling


The article is written by Enrique Santoyo-Brito, Matthew Anderson, and Stanley Fox, and was orignially published in the Journal of Herpetology.
Link to Article