The cardiac neural crest in Ambystoma mexicanum

To establish whether a region of the cranial neural crest contributes cells to the developing heart of Ambystoma mexicanum (axolotl), as it does in ma ny other vertebrates, we constructed a fate map for the neural crest in lat e neurula stage (stage 19-20) embryos. The fluorescent vital dye, Dil, was used as the lineage label. The various regions of the cranial neural folds were identified in relation to such landmarks as the developing forebrain, midbrain and hindbrain, and the appearance and extent of emerging somites. Labelled cells originating in the rhombencephalic region were found in the aortic arches and in the truncus arteriosus, and occasionally in the walls of the conus arteriosus. Cells were also found in the third and fourth bran chial arches. Labelled neural crest from the adjacent anterior trunk region appeared neither in the heart nor the visceral skeleton, whereas those fro m the mesencephalic region contributed to the first hypobranchial cartilage and to the first three branchial arches, but not to the heart. No labelled cells from any of the regions were seen in the ventricle or auricle.