ON A DYNAMIC REACTION-DIFFUSION MECHANISM - THE SPATIAL PATTERNING OFTEETH PRIMORDIA IN THE ALLIGATOR

It is now well established both theoretically and, more recently, expe rimentally, that steady-state spatial chemical concentration patterns can be formed by a number of specific reaction-diffusion systems. Reac tion-diffusion models have been widely applied to biological pattern f ormation problems. Here we propose a mode! mechanism for the initiatio n and spatial positioning of teeth primordia in the alligator, Alligat or mississippiensis, which, from a reaction-diffusion theory, introduc es, among other things, a new element, namely the effect of domain gro wth on dynamic spatial pattern formation. Detailed embryological studi es by Westergaard and Ferguson (B. Westergaard and M. W. J. Ferguson, J. Zool. Lend., 1986, 210, 575; 1987, 212, 191; Am. J. Anatomy, 1990, 187, 393) show that jaw growth plays a crucial role in the development al patterning of the tooth initiation process. Based on biological dat a we develop a reaction-diffusion mechanism, which crucially includes domain growth. The model can reproduce the spatial pattern development of the first seven teeth primordia in the lower half jaw of A. missis sippiensis. The results for the precise spatio temporal sequence compa re well with detailed developmental experiments.