The thermosensitive, or temperature-sensitive, period TSP is the period during development when sex is irreversibly determined. Developmental Dynamics. For example, in many turtle species, eggs from cooler nests hatch as all males, and eggs from warmer nests hatch as all females.
Nicole Valenzuela and Valentine Lance, 5—8. All crocodilians, most turtlesmany fishand some lizards exhibit TSD.
Sources Charnov, Eric, and James Bull. Skipper and T. This lizard requires bunchgrasses for cover and protection from predators and harsh winter conditions. Crews Medicine, Biology The Journal of endocrinology A slightly different example of this temperature-induced sex reversal is found in an Australian dragon lizard, which has the ZW system of sex chromosomes.
Archived from the original on The thermosensitive, or temperature-sensitive, period TSP is the period during development when sex is irreversibly determined. First, a gradient of males to females or females to males can be produced as the temperature changes from low to high, with each sex being exclusively produced on one of the two temperature extremes.
Although other environmental influences can have similar effects, temperature is the most wide-spread factor that alters aromatase activity and sex determination. Copy to Clipboard Reference Copied to Clipboard. Otherwise, population dynamics can be greatly affected by imbalanced sex ratios, abnormal offspring development and eventually species extinction that can result under extreme environmental conditions.
Consequently, the adaptive significance of TSD in all but the most recent origins of TSD may have been obscured by the passage temperature dependent sex determination in reptiles of arizona in Welland deep time, with TSD potentially being maintained in many amniote clades simply because it works 'well enough' i.
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.
Developmental Dynamics. Otherwise, population dynamics can be greatly affected by imbalanced sex ratios, abnormal offspring development and eventually species extinction that can result under extreme environmental conditions. However, further studies and information are needed to determine the possible effects of altered offspring development, including changes in body size and aggressive behaviour, on survival and reproductive success of reptile populations when offspring are incubated at either male- or female-biased temperatures.
Many reptile species, including sea turtles, leopard gecko Eublepharis macularius and Australian central bearded dragon lizard Pogona vitticeps ,were discovered exhibiting TSD which indicates that temperature is an extremely important factor for sex determination in reptiles Gutzke and Crews, , Quinn et al.
This increase in aromatase enables individuals to develop into males or females depending on the temperatures experienced.