Molecular adaptation mechanism of secondary aquatic life in cetaceans

Cetaceans are a unique group in the history of mammalian evolution owing to a series of evolutionary changes in morphology, anatomy, physiology, biochemistry and other aspects that have been generated during the return to water of their ancestors. Cetaceans therefore are the ideal models for studying the molecular mechanism of adaptation to a new environment. In this paper, the evolutionary genetic mechanisms of secondary aquatic adaptation in cetaceans in recent years are briefly reviewed, including body shape change, osmotic regulation, immune defense, dietary change, sensory system, and hypoxic tolerance. With the development of omics technology and their application, those potential functional regions and sites related to adaptive evolution based on bioinformatics analysis are needed to be tested using cell or animal models. These results will give us new insights into the molecular basis of secondary aquatic adaptation in cetaceans.