An aquaculture species raised on all continents, the rainbow trout is also a model organism for research, making it the most studied fish in the world. Its genome, decrypted at the Genoscope, is the first to be published for a representative of the family Salmonidae, which includes many species of great agricultural and ecological interest. Apart from the advances that can be expected regarding knowledge about trout and improved aquaculture practices, this sequencing had a major surprise in store for all geneticists.

About one hundred million years ago, the common ancestor of salmonids underwent a complete genome duplication. Such events have occurred repeatedly during the evolution of vertebrates (including within the lineage that led to humans), although most events occurred at much older dates. With trout, geneticists can see the consequences of a “recent” event for the first time, and observe the mechanisms of genetic evolution at work. Here, the general structure of the two copies of the original genome is still amazingly conserved, including the genes, indicating a slow and progressive reorganization. This result challenges the commonly accepted hypothesis in which the structure and content of genes evolves very rapidly following a genome duplication.