Comparative Genomics Analyses of Alpha-Keratins Reveal Insights Into Evolutionary Adaptation of Marine Mammals

The study analyzed α-keratin genes in 16 mammalian species, revealing significant gene loss and high pseudogenization rates in cetaceans compared to terrestrial artiodactylans, which likely contributed to their hairless phenotype as an adaptation to aquatic environments. Cetaceans showed an average of 37.29 α-keratin genes with a pseudogenization rate of 29.89%, while terrestrial artiodactylans had 58.33 genes with an 8.00% rate. Baleen whales retained more functional α-keratin genes due to their keratinized baleen. Pinnipeds, polar bears, and manatees had keratin gene numbers comparable to their terrestrial relatives, with manatees maintaining intact genes likely due to their bristles. Unique gene losses in cetaceans and manatees suggest convergent evolution towards hair loss for aquatic adaptation.