Spencer and Janzen found further support for the Charnov-Bull model by incubating painted turtles Chrysemys picta at different temperatures and measuring various characteristics indicative of fitness. Warner and Shine used hormonal manipulations to produce males and females across a range of temperatures in a species with TSD.
In the s, David Crews, a biologist at the University of Texas at Austinand colleagues found that some environmental pollutants caused sex-altering effects in turtles and other reptiles. Sexual differentiation humans Development of the reproductive system gonads Mesonephric duct Paramesonephric duct.
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.
Another hypothesis is that aromatase activity may be regulated by Sox9. Current research suggests that warming trends due to climate change may result in more female turtles being born!
There is only a small range of temperatures that permits both males and females to hatch from the same brood of eggs. Pieau and his colleagues focused on defining the TSD thermosensitive period, or the time of development during which changes in temperature can alter sexual organ growth. Nature has provided many variations on her masterpiece.
The thermosensitive, or temperature-sensitive, period TSP is the period during development when sex is irreversibly determined. The lizards were female in appearance and were capable of bearing offspring, despite having the ZZ chromosomes usually associated with male lizards.
In some species, including most mammals and insects, sex is determined solely by chromosomes; in other species, sex is a matter of environmental conditions. Another example in which sex determination is affected by the location of the organism is the case of the slipper snail Crepidula fornicata.
Similarly, the Southern brook lamprey, Ichthyomyzon gageiand the eels, including the American eel, Anguilla rostratawere not included because the circumstantial evidence available so far points to growth-dependent sex differentiation  rather than to TSD in these species .
Nicole Valenzuela and Valentine Lance, 21— While aromatase activity remains low for much of development in individuals that exhibit TSD, during the thermosensitive period, variations in temperature increase the activity of aromatase.
Conclusions In this study, we performed an analysis of field and laboratory data related to fish species for which TSD was assumed. Studying the spotted skink, they observed that the highland population was not affected by temperature, yet, there was a negative correlation between annual temperature and cohort sex ratios in the lowlands.
J Endocrinol 1—8. This page uses Creative Commons Licensed content from Wikipedia view authors. Can J Zool —
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.
Annual Review of Genetics. Other reptiles governed by GSD have a system, similar to one found in birds, with Z and W sex chromosomes.