Molar Histology in Mangabeys and Guenons: Exploring the Relationship Between Enamel Prism Angle Variation and Diet

Abstract

Understanding relationships between diet and tooth structure is of central concern in biological anthropology. Such relationships form the basis of dietary inference for fossil species. It has been suggested that the angle at which tooth enamel prisms approach tooth wear surfaces may be associated with different foods types. High angles have been hypothesized to confer greater enamel stiffness and are thought to be associated with hard-object feeding, or durophagy. Conversely, low angles are thought to confer abrasion resistance, which could indicate abrasive foods and/or grit adhering to foods. We investigated prism angles in molars of two extant mangabey species’ samples: Lophocebus albigena and Cercocebus atys, whose diets are documented by extensive field data. L. albigena prefer soft fruits, falling back on hard seeds during periods of scarcity. By contrast, C. atys feeds on hard seeds year-round. For comparison, we investigated prism angles in Cercopithecus cephus, C. diana and C. petaurista, none of which consume hard foods. Molars were sectioned using standard protocols and imaged with a Motic BA 310 Microscope with a Moticam camera. ImageJ FIJI was used to measure prism angles relative to wear surfaces on “functional” cusps (i.e., those involved in crushing and grinding). Our results show that upper functional cusp angles of C. atys (N = 13) averaged 55.3 degrees, those of L. albigena (N = 11) averaged 39.5 degrees, and those of the pooled Cercopithecus sample (N = 11) averaged 37.0 degrees. A repeated measures regression analysis of upper functional cusps was used to test for fixed effects of tooth, genus, and tooth-genus interaction on prism angle. Only genus was found to be statistically significant. Pairwise comparisons from this model revealed statistically significant differences in prism angles between C. atys and L. albigena as well as between C. atys and the pooled Cercopithecus sample. There was no statistically significant difference between L. albigena and Cercopithecus. These results suggest that the prism angles of a fallback hard-object feeder can be more similar to those of soft-object feeders than to those of an habitual hard-object feeder, indicating that the correspondence between durophagy and enamel microstructure is not straightforward.No embargoAcademic Major: Anthropolog