Evolution of the neural crest.

The recent advances in studies of the neural crest in vertebrates and the analysis of basal chordates using molecular and embryological approaches have demonstrated that at least part of the genetic programs and the cellular behavior were in place in nonvertebrate chordates before the neural crest evolved. Nevertheless, both the missing aspects and the close similarities found could explain why basal chordates lack a bona fide neural crest population, even though some migratory neurons and pigment cells have been recently identified in ascidians and amphioxus.