Histomorphological age changes associated with growth and development of the femur in Saguinus fuscicollis and Saguinus oedipus (Callitrichidae, Primates)

Although skeletal histology has been investigated for a number of primate species, only for humans has research been in depth enough to adequately document specific histomorphological changes with age. In fact, our knowledge of comparative ageing in nonhuman primate skeletal histology is almost nonexistent.

This study documents histological age changes in the femoral midshaft of the South American tamarin, genus Saguinus. Examined were 86 Saguinus fuscicollis and 26 S. oedipus age and sex documented specimens. The entire approximate 13 year life span of these primates is represented within the sample. Two histomorphological aspects were investigated, the change in total cortical area and associated dimensions, as well as the pattern of osteonization or remodeling.

Results of this research indicate that although there are differences between the two species in cortical area expansion and patterning of osteonization, they conform to traditional growth curves for primate species. Cortical stability was evident for the posterior and medial quadrants of the bone due to posteriomedial muscular attachment, while cortical drift occurred anteriolaterally. The trends of intracortical remodeling are such that specific techniques of age determination from the quantification of microstructures (i.e., osteons, osteon fragments) are not applicable. Due to continual cortical involution, most evidence of prior intracortical remodeling is lost in old age. Osteonization in older specimens was found to be limited to the posterior quadrant of the femur, indicating remodeling due to muscle stress rather than remodeling of compression.