Morphogenetic studies on the neural crest of hynobius larvae using vital staining and India ink labeling methods

The neural crest cells of hynobius larvae during the morphogenesis of the neural crest were studied with the following methods: the region of the primordial neural crest was first determined by vital stainings, and then the movement of individual neural crest cells was traced with India ink labeling. The cytoarchitecture and the fine structure of neural crest cells were further observed by light, transmission and scanning electron microscopy. The primordium of the neural crest is located in the area extending from the lateral part of the neural plate to the medial part of the neural fold. RAVEN (1931) suggested that the lateral part of the neural fold was a part of the primordial neural crest. The result of our vital staining shows that it is the primordial epidermal ectoderm. The morphogenesis of the neural crest was found to proceed as follows: at first both neural folds moved to the dorsal mid line of larva, then contacted and fused to each other. The primordial neural crest cells in the neural folds became polygonal, and these cells from both folds mixed and formed a neural crest cell mass. In this process they lost their junctional apparatuses. When larvae developed at the tail bud stage, the cells in the lateral part of the neural crest extended their cytoplasmic processes and began to migrate.