Large scale gene duplication affected the European eel (Anguilla anguilla) after the 3R teleost duplication

Genomic scale duplication of genes generates raw genetic material, which may facilitate new adaptations for the organism. Previous studies on eels have reported specific gene duplications, however a species-specific large-scale gene duplication has never before been proposed. In this study, we have assembled a de novo European eel transcriptome and the data show more than a thousand gene duplications that happened, according to a 4dTv analysis, after the teleost specific 3R whole genome duplication (WGD). The European eel has a complex and peculiar life cycle, which involves extensive migration, drastic habitat changes and metamorphoses, all of which could have been facilitated by the genes derived from this large-scale gene duplication. Of the paralogs created, those with a lower genetic distance are mostly found in tandem repeats, indicating that they are young segmental duplications. The older eel paralogs showed a different pattern, with more extensive synteny suggesting that a Whole Genome Duplication (WGD) event may have happened in the eel lineage. Furthermore, an enrichment analysis of eel specific paralogs further revealed GO-terms typically enriched after a WGD. Thus, this study, to the best of our knowledge, is the first to present evidence indicating an Anguillidae family specific large-scale gene duplication, which may include a 4R WGD.