Résumé
Solitary ascidians belong to the tunicate phyla and were the first animals used by experimental embryologists. This chapter, dedicated to these organisms, points out the several advantages offered by the solitary ascidians in modern biology, especially through the combined knowledge of 13solitary ascidians species genomes, of large amount of transcriptomic data and of several available molecular tools to study gene function. Furthermore, this chapter references the databases that emerged in this research field which facilitate comparative genomics studies within ascidians but also between chordates. We include a large overview of the general biological features of these organisms such as geographical distribution, life cycle and embryogenesis, with a focus on developmental differences between species. Finally, some challenging questions are discussed, with a special emphasis on the unique opportunity given by ascidian embryos to serve as the basis for a global computational model of chordate embryogenesis.