Epigenetics in sex determination and differentiation of fish

Sex determination and differentiation are universal biological phenomena in animals. The sex determination mechanisms in fish are diverse among species and can be mainly divided into two categories, genetic sex determination (GSD) and environmental sex determination (ESD). In species with GSD, the sex is determined by heritable genetic components, while in species with ESD, the sex is controlled by environmental factors. The phenotype of fish is the result of the interaction between environment and genetics. Epigenetics serves as a bridge-connecting environment and genotype, and its role in fish sex determination and differentiation is the subject of a lot of research. In this chapter, we focus on epigenetics in fish sex determination and differentiation. We first briefly review the role of epigenetics in sex chromosome evolution, and then the role of epigenetics in sex determination and differentiation is summarized for both gonochoristic and hermaphroditic species. Afterward, the transgenerational epigenetic regulation mechanism in sex reversal, which focuses on the inheritance of epigenetic patterns across one or more generations, is discussed. At the end of this chapter, we summarize and provide some insights into the future perspectives of research on epigenetics in sex determination and differentiation of fish. The study of epigenetics of sex determination and differentiation has significance for both basic research and applications in aquaculture.