ABSTRACT
Cephalochordates, also called lancelets or amphioxus, belong to the chordate group along with vertebrates and tunicates. Chordates are characterized by conserved anatomical features during at least some period of their life cycle such as the notochord, a dorsal nerve cord, segmented muscles and a post anal tail. Amphioxus morphology, developmental modalities and genome organization are thought to have derived relatively little compared to the chordate ancestral state, making these animals good models to understand the evolution of developmental mechanisms that led to the appearance of vertebrate novelties. This chapter presents basic knowledge about the biology of amphioxus as well as major discoveries and future challenges. Although amphioxus was already recognized as key for our understanding of vertebrate complexity by 18th-century zoologists, the recent development of new sequencing techniques, powerful approaches to analyzing genome organization and improved mutagenesis tools will certainly reinforce its position as an essential evo-devo model.
