Meeting Abstract
110.5 Sunday, Jan. 6 Mouse Jaw Ontogeny in Tres Partes Divisa Est SWIDERSKI, D. L.*; ZELDITCH, M. L.; Univ. of Michigan, Ann Arbor; Univ. of Michigan, Ann Arbor dlswider@umich.edu
The mouse mandible is a popular model system that continues to be the focus of studies in evo-devo and other fields. Yet, little attention has been given to the role of postnatal growth in producing the adult form. Using cleared and stained specimens, we describe the timing of tooth and jaw development and changes in jaw size and shape from postnatal day 1 (p1) through weaning (c. p21) to adulthood (c. p35). We found that tooth development is relatively advanced at birth, and that the functional adult dentition is in place by p15 (just before the start of weaning). Shape analysis showed that the trajectory of jaw shape changes direction at least twice between birth and adulthood, with the first change around p7 and the second around p15. Before p7, the tooth bearing horizontal ramus deepens more than it elongates while the bone keeps pace with the growing molar crowns; the posterior processes also expand rapidly, increasing space for muscle attachment well in advance of the shift from nursing to chewing. After p7, the ramus deepens more slowly, with the teeth erupting while the roots are still growing; and the posterior processes widen more than elongate. After p15, the ramus increases curvature with the incisor, while the main changes in the posterior processes are deepening of the angular and elongation of the coronoid. Thus, at each stage there are changes in shape to all tooth and muscle bearing regions, and at each change of direction, all regions change their pattern of growth. In each interval (p1-7, 7-15, 15-35), the amount of shape change is nearly the same, as is the amount of size change. So although the jaw and teeth are close to adult form at the end of weaning, this last phase still affords ample opportunity for the environment to exert a direct effect on jaw size and on the shapes of all parts of the jaw.
