Role of the neural crest in development of the cartilaginous cranial and visceral skeleton of the medaka, Oryzias latipes (Teleostei).

Neural crestectomies were performed on neurula stage medaka embryos to remove neural crest with tungsten needles from one of five anteriorly located zones. The embryos were allowed to develop to stage 35 (immediately posthatching) larvae, then cleared and stained for cartilage. An analysis of changes to the head skeletons indicated that most of the anterior neurocranium and the entire viscerocranium received neural crest contributions during development. The elements involved included; the lamina orbitonasalis of the nasal capsule, the trabeculae, Meckels' cartilage and the quadrate of the lower jaw, the pterygoid process, the orbital cartilages and the epiphyseals of the neurocranial roof, as well as all the elements of the hyoid and branchial arches. By further analysis of only those neural crest ablations which produced alterations to the head skeleton, the neural crest cells which contributed to the development of each element were mapped. They originated principally, from one of three regions; the mesencephalon (second most anterior zone removed, number II), the preotic rhombencephalon (zone III), or the postotic rhombencephalon (zone IV). Neural crest from the level of the prosencephalon (zone I) was not chondrogenic nor was neural crest from the fifth region (zone V) which extended beyond the 5th to about the 8th or 10th somite and marked the anterior end of trunk neural crest. The data are discussed and are found to be consistent with the results from other vertebrates and support the central role of the neural crest in the development and evolution of the vertebrate head skeleton.