Mobile Elements in Ray-Finned Fish Genomes

Ray-finned fishes (Actinopterygii) are a very diverse group of vertebrates, encompassingspecies adapted to live in freshwater and marine environments, from the deep sea to highmountain streams. Genome sequencing offers a genetic resource for investigating the molecularbases of this phenotypic diversity and these adaptations to various habitats. The wide range ofgenome sizes observed in fishes is due to the role of transposable elements (TEs), which arepowerful drivers of species diversity. Analyses performed to date provide evidence that class IIDNA transposons are the most abundant component in most fish genomes and that compared toother vertebrate genomes, many TE superfamilies are present in actinopterygians. Moreover,specific TEs have been reported in ray-finned fishes as a possible result of an intricate relationshipbetween TE evolution and the environment. The data summarized here underline the biologicalinterest in Actinopterygii as a model group to investigate the mechanisms responsible for the highbiodiversity observed in this taxon.