The evolutionary origin and diversification of the vertebrate olfactory system

Abstract

When and how did the vertebrate olfactory system evolve? The closest relatives of vertebrates, such as tunicates and amphioxus, lack distinct olfactory organs, suggesting that the vertebrate olfactory system evolved independently within the vertebrate lineage. Cyclostomes, including lampreys and hagfish, represent the basal lineages of the vertebrates and provide valuable insights into early vertebrate evolution. Comparison of the olfactory receptors, cells, and circuits between cyclostomes and other vertebrates reveals both similarities and differences in the olfactory system, shedding light on the evolutionary origin and diversification of the vertebrate olfactory system.