Degenerins and amiloride-sensitive Na+ channels form a new family of cationic ion channels (DEG/NaC). DEG/NaC family emerged as common denominator within a metazoan mechanosensory apparatus. In this study, we characterized a new member of such family in amphioxus, Branchiostoma floridae. The AmphiNaC cDNA sequence encodes a protein showing amino acid residues characteristic of DEG/NaC family, such as two hydrophobic domains surrounding a large extracellular loop that includes cystein-rich domains; nevertheless its predicted sequence is quite divergent from other family members. AmphiNaC is expressed at early larval stage in some putative sensory epidermal cells in the middle of the body and in neurons of the posterior cerebral vesicle, as well as in some ventrolateral and mediolateral neurons of the neural tube. In late larvae, AmphiNaC expression is maintained in some neurons of the neural tube, and it is expressed in putative sensory epidermal cells of rostrum and mouth. The analysis of AmphiNaC gene expression pattern suggests that it might be involved in neurotransmission and sensory modulation.