Environmental Control of Sex Determination and Differentiation in Reptiles

Abstract

Most vertebrates use a genetic sex determination system, whereas a diverse set of reptile taxa use an environmental sex determination system – more specifically, a temperature-dependent sex determination (TSD) system. The TSD system is where sex is established by the incubation temperature during a critical stage of embryonic development. It has been almost a half century since the first TSD system was found in a lizard species. Thermal effects on sex determination have been described in many other reptile species since then. TSD has been found in all crocodilians and tuataras examined and in most turtles and some lizards. However, clarification is needed about this unique mode of sex determination in reptiles, in particular, factors triggering the intrinsic genetic cascade, which leads either to development of a testis or ovary. In several instances, TSD has evolved separately in reptilian lineage and, therefore, the adaptive significance of TSD is an attractive topic from an evolutionary view. In this chapter, the general background and recent advancements for TSD research in reptiles is discussed.