Journal of Evolutionary Biology. Download as PDF Printable version. Skip navigation. An Introduction to Behavioral Endocrinology.
The lizards were female in appearance and were capable of bearing offspring, despite having the ZZ chromosomes usually associated with male lizards. Guillette Jr. Gilbert SF. Charnier, Madeline. Spencer and Janzen found that hatchlings from mixed-sex nests were less energy efficient and grew less than their same-sex counterparts incubated in single-sex producing temperatures.
The next phase can be either male or female, depending on the animal's position in the mound.
At certain levels of PCBs, the feminizing effects can override the influence of temperature, negating the effects of TSD in an organism. In future, we would like to know how an unstable environmental factor such as incubation temperature was able to establish itself as a sex determination factor. This knowledge may have important consequences in environmental conservation efforts to protect endangered turtle species.
However, there is evidence that during climactic extremes, changes in the sex determining mechanism itself to GSD are selected for, particularly in the highly-mutable turtles. However, in the lowlands, temperatures are more constant and a longer activity season allows for favorable conditions for TSD.
Scientists are still working to understand the evolution of TSD and the implications of climate change for species that exhibit this mechanism of sex determination. The evolutionary advantages and disadvantages of temperature-dependent sex determination are discussed in Chapter
Between these extremes, males predominate. A study found that hot temperatures altered the expression of the sex chromosomes in Australia's bearded dragon lizards. ScienceDaily, 23 December Similarly, injecting eggs with inhibitors of estrogen synthesis will produce male offspring, even if the eggs are incubated at temperatures that usually produce females Dorizzi et al.
Environmental Sex Determination - Developmental Biology.