After this period, however, sex reversal is impossible. TSD may be advantageous and selected for in turtles, as embryo energy efficiency and hatchling size are optimized for each sex at single-sex incubation temperatures and are indicative of first-year survivorship.
Similarly, the presence of large numbers of males will cause some of the males to become females. Sex determination and differentiation. This sex-determining gene is seen throughout the vertebrates, where its expression in gonads correlates extremely well with the production of testes.
It appears that the enzyme aromatase which can convert testosterone into estrogen is important in temperaturedependent sex determination.
Those crocodilians which are incubated and grow to maturity under optimal environmental conditions will be both large and male. Crockett, George W. ScienceDaily, 23 December The kill zone is an arc traced by the head and neck, although some species literally dive onto prey just below the surface.
Typically bright yellow or orange, the tongue's color may provide a social or warning signal when the jaws gape. Although the nictitating membrane is transparent except for the ossified leading edge, crocodilians still see poorly through it.
ScienceDaily, 23 December Figure The lizards were female in appearance and were capable of bearing offspring, despite having the ZZ chromosomes usually associated with male lizards. The Journal of Experimental Zoology. After these molluscs become female, they will be fertilized by the male above them.
Hormones and temperature show signs of acting in the same pathway, in that less hormone is required to produce a sexual shift as the incubation conditions near the pivotal temperature. Bibcode : Natur.
Journal Information Scientific Reports 5, Article number: doi Other work centers on a theoretical model the Charnov — Bull model ,   predicted that selection should favour TSD over chromosome -based systems when "the developmental environment differentially influences male versus female fitness";  this theoretical model was empirically validated thirty years later  but the generality of this hypothesis in reptiles is questioned.
Temperature-dependent aromatase activity is also seen in diamondback terrapins, and its inhibition masculinizes their gonads Jeyasuria et al.