Temperature-dependent sex determination

Temperature-dependent sex determination (TSD) is a type of environmental sex determination in which the temperatures experienced during embryonic/larval development determine the sex of the offspring. It is contrasted with genotypic sex determination, which is determined by the inheritance of certain genes.

Overview

TSD is common in reptiles, but also occurs in some fish and invertebrates. The specific temperatures required for male or female sex determination vary widely among species. In many turtle species, for example, lower temperatures produce males and higher temperatures produce females. However, in the American alligator and some turtles, intermediate temperatures produce males and both high and low temperatures produce females.

Mechanism

The exact mechanism of TSD is not well understood, but it is thought to involve the expression of temperature-sensitive genes during a critical period of development. These genes may control the production of sex hormones or other factors that influence the development of the sex organs.

Evolution

The evolution of TSD is also not well understood. One theory is that it provides a way for species to adapt to changing environmental conditions. For example, in a warming climate, a species with TSD could produce more females, leading to a higher reproductive rate.

Impact of Climate Change

Climate change poses a significant threat to species with TSD. Rising global temperatures could skew sex ratios, potentially leading to population declines or even extinction. Conservation efforts for these species must therefore take into account the impact of temperature on sex determination.

See Also

• Sex determination system
• Environmental sex determination
• Genotypic sex determination