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Observations on the migration and differentiation of neural crest cells in somite extirpated salamander larvae.

In order to research the influences of the somites or their derivatives on the migration and differentiation of neural crest cells, unilateral extirpation of somites was performed in the larvae of the salamander (Hynobius lichenatus Boulenger). Two types of neural crest cells appeared in the somite-free environment. They could already be distinguished from each other shortly after beginning of migration. One type of the cells was distributed in the expanded space between the epidermis and the neural tube, with melanocytes differentiated from them. The other type of the cells migrated closely to the lateral wall of the neural tube. They aggregated as a cord on the ventrolateral side of the neural tube and gave rise either to neurons or to satellite cells of spinal ganglia. The sequence of cytological events along the development of the cells and the time required for each event were essentially identical with those of the melanocytes and spinal ganglion cells developing on the control side. The present results suggest not only that migration and differentiation of neural crest cells are independent of the possible regulation of the somites or their derivatives but also that the fate of neural crest cells is determined before the onset of migration.