Abstract: The diversity of inputs that guide sexual fate during development is both intriguing and daunting. Reptiles,as poikilothermal animals,differing from mammalian conservative genotypic sex determination （GSD）,are in the transition period of environmental sex determination （ESD）and GSD. Its sex determination is sensitive to environmental factors,such as temperature and contaminants. Pelodiscus sinensis,a precious aquatic economic animal,is of great significance in research on sex determination in reptile biology. With further research on the machinery of sex determination in P. sinensis over the world,several studies have provided evidence of P. sinensis can be classified as temperature-dependent sex determination（TSD）,largely due to the sex ratio can be truly impacted by temperature;however,the results still vary,20%-30% individuals fail to develop along the direction of temperature. Second,the sex determination mode of P. sinensis is generally categorized as GSD,as evidenced by the existence of heteromorphic ZZ/ZW micro-sex chromosomes. However,little is known about the exact genetic mechanisms. In addition,many previous reports have focused on conserved genes with known function in sexual differentiation across vertebrates,such as Dmrt1,Sox9,Mis,Amh,Cyp19a1 and Foxl2,very few other genes have been investigated in detailed,leading to a limited understanding of overall gene expression throughout TSD. Furthermore,exogenous hormones have been demonstrated to induce sex direct differentiation during a specific embryonic period known as the temperature sensitive period（TSP）. Taking all together,these results indicate that the boundary line between GSD and ESD is blurred,a critical question of exactly how temperature cues and sex hormones trigger sex development has remained open. This review provides coherent information on the recentlydiscovered mechanisms underlying reptiles sex determination,aiming at overcoming the single breeding technology and providing scientific basis for the selection of high-quality breeding in P. sinensis.

Key words: Pelodiscus sinensis, sex determination, sex differentiation, temperature sensitive period, exogenous hormones