Bone remodeling is reduced in high stress regions of the cercopithecoid mandible

Independent lines of evidence suggest that osteonal bone remodeling is a function of both mechanical (i.e., changes in stress) and non-mechanical (i.e., metabolic needs related to calcium liberation) factors. The degree to which secondary bone reflects mechanical factors, however, is incompletely understood despite the common assumption that the stress environment mediates remodeling activity. Here, we investigate whether there are remodeling differences between regions of primate mandibular bone known to have distinct stress environments.

Osteon density, osteon fragment density, and relative osteonal area are measured as indicators of remodeling activity from postcanine and symphyseal thin sections of four sympatric monkey species (N = 20 total) from Taï Forest, Côte d'Ivoire: Piliocolobus badius, Colobus polykomos, Cercocebus atys, Cercopithecus diana. Subfamily and regional effects were assessed by two-way ANOVA.

Symphyseal bone has lower osteonal density, fragment density and relative osteonal area than postcanine bone in all species, indicating relatively low remodeling activity in symphyseal bone, despite the likelihood of relatively high stresses in its lingual cortex. Subfamily differences in postcanine remodeling are significant in that colobines exhibit greater remodeling than cercopithecines.

The data suggest that high strains are not requisite for bone remodeling. How the lingual symphysis negotiates a high strain environment without the reparative benefit of remodeling is yet to be elucidated, but the data prompt reevaluation of the relationship of targeted remodeling to stress histories. Differences in osteonal bone density between taxa might reflect feeding or dietary influences on remodeling activity, but sample composition prevents parsing behavioral from other taxon-specific effects.