Cranial neural crest cell migration in the Australian lungfish, Neoceratodus forsteri

A crucial role for the cranial neural crest in head development has been es tablished for both actinopterygian fishes and tetrapods. It has been claime d, however, that the neural crest is unimportant for head development in th e Australian lungfish (Neoceratodus forsteri), a member of the group (Dipno i) which is commonly considered to be the living sister group of the tetrap ods. In the present study, we used scanning electron microscopy to study cr anial neural crest development in the Australian lungfish. Our results, con trary to those of Kemp, show that cranial neural crest cells do emerge and migrate in the Australian lungfish in the same way as in other vertebrates, forming mandibular, hyoid, and branchial streams. The major difference is in the timing of the onset of cranial neural crest migration. It is delayed in the Australian lungfish in comparison with their living sister group th e Lissamphibia. Furthermore, the delay in timing between the emergence of t he hyoid and branchial crest streams is very long, indicating a steeper ant erior-posterior gradient than in amphibians. We are now extending our work on lungfish head development to include experimental studies (ablation of s elected streams of neural crest cells) and fate mapping (using fluoresent t racer dyes such as DiI) to document the normal fate as well as the role in head patterning of the cranial neural crest in the Australian lungfish.