Epigenetics in Hybridization and Polyploidization of Aquatic Animals

Hybridization and polyploidization are considered the main drivers of speciation. Either due to the conflict between parental genomes or chromosome imbalances, the resulting hybrids or polyploids frequently undergo "genomic shock" and experience rapid genetic and epigenetic modifications through hybridization and polyploidization. This phenomenon is thought to have given rise to the origin of evolutionary innovations. Meanwhile, hybridizing and polyploidy breeding are two of the most popular genetic breeding biotechnologies applied in aquatic animals. Recent 'omic studies in hybrids and polyploids have provided new insights into the consequences of hybridization and polyploidization. We will first introduce the definitions, consequences, and advantages of hybridization and polyploidization, then summarize the recent advances in the epigenetic changes and effects during hybridization and polyploidization in aquatic animals, focusing on nonadditive gene expression, DNA methylation, histone modifications, miRNA, and the role of epigenetics in heterosis. Finally, some main research trends on epigenetics in the hybridization and polyploidization of aquatic animals will be discussed. Future studies on the epigenetic consequences of hybridization and polyploidization can help us understand why aquatic polyploids or hybrids possess rapid growth, extensive adaptability, and disease resistance, and will open a door to develop novel biotechnologies, such as epigenetic selection and key epigenetic mark editing, to breed improved aquatic varieties.