Significance of Heterochronic Differences in Neural Crest Cell Migration and Sclerotomal Development in Evolution of the Trunk Body Organization from Agnathans to Gnathostomes

Abstract

Abstract The process of neural crest cell migration differs between the lamprey and swordtail [Hirata et al., Zoological Science 14: 305-312 (1997)]. In swordtail embryos, neural crest cells in the ventral pathway are distributed ventrally beyond the notochord at all axial levels of the trunk. In contrast, no neural crest cells are seen ventrally beyond the notochord in post-branchial regions of lamprey embryos, although in the branchial regions some cells migrate ventrally beyond the notochord. Since sclerotomal development is essential in the formation of ventral pathways in avian and mammalian embryos, sclerotomal development in lamprey and swordtail embryos was examined to understand the mechanism underlying the differences in neural crest cell migration between these two animals. Sclerotomal development and neural crest cell migration progressed concurrently in the swordtail trunk. In the lamprey, the formation of the sclerotome was regionally different along the antero-posterior axis. In the branchi...