Neural crest derivation of the bony skull of the Mexican axolotl

Contributions of the cranial neural crest to cartilages and bones of the skull have been revealed in great detail in one amniote model using the quail‐chick‐chimeric system. Yet, the extent to which patterns of embryonic derivation are evolutionary conserved or labile remains an intriguing question, given the extensive variability in skull morphology observed among craniates. Amphibians are a non‐amniote tetrapod group with a highly derived skull morphology and ontogeny. Recent technical advances now enable us to derive fate maps at a level of detail previously known only from avian studies. We employ embryonic transplantations, using GFP‐transgenic axolotls as donors, to document the nature and extent of neural crest contribution to the adult osteocranium. Comparison of axolotl with results available from chicken, mouse and Xenopus reveals that different species show mosaics of conserved and variable patterns of embryonic derivation. The recently reported rostral inversion of neural crest‐derived adult cartilages in Xenopus is not a feature common to all amphibians, but instead may be uniquely associated with the extreme posthatching metamorphosis characteristic of most anurans. Grant Funding Source : MCZ