Pough, F. Temperature-dependent sex determination in reptiles Location-dependent sex determination in Bonellia and Crepidula. The lizards were female in appearance and were capable of bearing offspring, despite having the ZZ chromosomes usually associated with male lizards.
Sinauer Associates: Massachusetts. Young individuals are always male. All crocodilians, most turtlesmany fishand some lizards exhibit TSD. Warner and Shine used hormonal manipulations to produce males and females across a range of temperatures in a species with TSD.
Nicole Valenzuela and Valentine Lance, 5—8. This is called temperature-dependent sex determination, or TSD. The distinction between chromosomal sex-determination systems and TSD is often blurred because the sex of some species — such as the three-lined skink Bassiana duperreyi and the central bearded dragon Pogona vitticeps — is determined by sex chromosomes, but this is over-ridden by temperatures that are tolerable but extreme.
Young individuals are always male. The number of males and females in a population is the sex ratio, a key demographic parameter crucial for population viability.
Conservation Biology. This sex-determining gene is seen throughout the vertebrates, where its expression in gonads correlates extremely well with the production of testes. Cite this Page Gilbert SF. Estrogen can override temperature and induce ovarian differentiation even at masculinizing temperatures.
They concluded that this differentiation in climate causes divergent selection on regulatory elements in the sex-determining network allowing for the emergence of sex chromosomes in the highlands.
In Emys, the last third of development appears to be the most critical for sex determination. More examples of context-dependent sex determination will be studied in Chapter Washington: Smithsonian Books, Note: Content may be edited for style and length. Temperature-dependent aromatase activity is also seen in diamondback terrapins, and its inhibition masculinizes their gonads Jeyasuria et al.
This evolutionary model, called the Charnov-Bull model, outlines the conditions under which the evolution of environmental sex determination occurs, and scientists later applied it to vertebrates with TSD.