Adaptive Plasticity in the Mammalian Masticatory Complex: You AreWhat, and How, You Eat

Phenotypic Plasticity and Function of the Hard Palate in Growing Rabbits

“…Such studies demonstrate that the external dimensions, cortical bone thickness, trabecular density, and cartilage composition of nondental mandibular elements are influenced significantly by ontogenetic variation in masticatory peak and/or cyclical loads during an organism's lifetime. In this regard, masticatory elements appear to show similar patterns of plasticity as observed in postcranial tissues and structures Hylander, 1981, 1982;Lanyon and Rubin, 1985;Biewener, 1993;Ravosa et al, 2007bRavosa et al, , 2008b.…”

“…As the between-cohort comparisons largely accentuate the duration of oral processing (i.e., crushed pellets exhibit similar properties to whole pellets), under-use diet rabbits are posited to more closely resemble normal/non-pathological loading conditions. Indeed, unlike the jaw joints of over-use diet rabbits, the anatomy of under-use diet rabbits is similar to that for a limited number of 6-month old adult rabbits raised on a ''normal/control'' diet of intact pellets (Ravosa et al, 2008b).…”

“…This is in accord with indirect evidence from finite element analysis that a vertically thickened hard palate is part of a suite of cranial features that may act to resist strains resulting from elevated masticatory stresses (Strait et al, 2007). Indeed, paleobiological arguments that do not consider the role of diet-induced plasticity in adaptive explanations for all aspects of hominin feeding anatomy (e.g., Ungar and Scott, 2008, and a related article by Gibbons, 2008) overlook the significant influence of long-term mechanical loading on the patterning of craniomandibular form throughout an organism's lifetime (Ravosa et al, 2008b). From a paleontological and ecomorphological perspective, experimental analyses that strive to more closely model masticatory forces experienced throughout an organism's lifetime will be critical for more accurately characterizing regional and temporal effects on craniomandibular form and function.…”

Teaching an old jaw new tricks: Diet-induced plasticity in a model organism, from weaning to adulthood

“…By contrast, preliminary observational data from a sample of 12 adults indicate that rabbits use approximately three times more chewing cycles per unit food mass when processing hay versus pellets (2.95 times more chews per g, 95% confidence interval: 2.58-3.35) (unpublished results), indicating that hay consumption does engender greater repetitive loading and correspondingly longer loading durations. Given the adaptive role of increased cyclical loading in bone formation (Bouvier and Hylander, 1981;Biewener et al, 1986), hay consumption should thus stimulate osteogenesis and result in larger jaw proportions in the two experimental groups in comparison with the control rabbits (Ravosa et al, 2007;Ravosa et al, 2008;Menegaz et al, 2009;Scott et al, 2014). With respect to differences between the experimental groups, we predicted an inverse relationship between age and the magnitude of diet-induced osteogenic responses; in other words: early rabbits at week 6>late rabbits at week 24>early rabbits at week 30>late rabbits at week 48.…”

“…Menegaz et al, 2009;Holmes and Ruff, 2011;Scott et al, 2014;Standen et al, 2014). The way in which bone responds to loading over the course of an organism's lifetime is complex and multileveled (Bertram and Swartz, 1991;Hsieh et al, 2001;Pearson and Lieberman, 2004;Hamrick et al, 2006;Ruff et al, 2006;Ravosa et al, 2008;Ravosa et al, 2010b). Several studies have observed an age-related decrease in the ability of an organism to modify a bone's cross-sectional geometry adaptively (i.e.…”