Internal architecture of the mandibular condyle of rabbits is related to dietary resistance during growth

Although there is considerable evidence that bone responds to the loading environment in which it develops, few analyses have examined phenotypic plasticity or bone functional adaptation in the masticatory apparatus. Though prior work suggests that masticatory morphology is sensitive to differences in food mechanical properties during development, the importance of the timing/ duration of loading and variation in naturalistic diets is less clear. Here we examine micro- and macrostructural differences in the mandibular condyle in four groups of white rabbits (Oryctolagus cuniculus) raised for a year on diets that varied in mechanical properties and timing of the introduction of mechanically challenging foods, simulating seasonal variation in diet. We employ sliding semilandmarks to locate multiple volumes of interest deep to the mandibular condyle articular surface, and we compare bone volume fraction, trabecular thickness and spacing, and condylar size/shape among experimental groups. Results reveal a shared pattern of bony architecture across the articular surface of all treatment groups, while also demonstrating significant among-group differences. Rabbits raised on mechanically challenging diets have significantly increased bone volume fraction relative to controls fed a less challenging diet. The postweaning timing of the introduction of mechanically challenging foods also influences architectural properties suggesting that bone plasticity can extend well into adulthood and that bony responses to changes in loading may be rapid. These findings demonstrate that bony architecture of the mandibular condyle in rabbits responds to variation in mechanical loading during an organism9s lifetime and has the potential to track dietary variation within and among species.