Horizontal gene transfer (HGT) is the acquisition of genetic material from non-parent organisms of different species, by opposition with vertical gene transfer where the genetic material is inherited from the parents. While this process is widely described in prokaryotes where it has been shown to accelerate their evolution, the impact of HGT on the evolution of eukaryotes, and particularly on metazoans, remains a relatively unexplored field of research. In collaboration with the team of Dr. Simon Blanchoud (University of Fribourg, Switzerland) we began to investigate the extent and the nature of HGTs in Tunicates. We will take advantage of a recent and significant increase of genomic data that covers almost the whole taxon, as well as of the development of novel algorithmic tools, to perform an exhaustive and consistent analysis of HGT. Tunicates present one of the best-documented case of active HGT in metazoans, cellulose synthase. Preliminary proteomic studies have identified chemical compounds similar to some known plant secondary metabolites, suggesting a co-option of vegetal biosynthetic pathways, potentially through HGTs. Therefore, Tunicates provides a unique opportunity to study the distribution and the potential function of HGTs in chordates and eventually to integrate these results with the metabolic, physiologic, and developmental specifics of these animals.