Comparative Anatomy of Bat Jaw Musculature via Diffusible Iodine-Based Contrast-Enhanced Computed Tomography

Abstract

Noctilionoid bats exhibit an extraordinary array of cranial specializations that match diverse diets, including variation in jaw musculature physiological cross-sectional areas (PCSA), lever arms, and relative contribution to bite force. Although previous research in this group has linked variation in skull shape and muscle mechanics to biting performance, there are still important gaps about the anatomical underpinnings of noctilionoid dietary adaptations, including the degree of compartmentalization of the jaw musculature, and whether and how muscle attachment sites have evolved across noctilionoid species that specialize on derived diets. Here, we paired dissections with Diffusible Iodine-based Contrast-Enhanced Computed Tomography (diceCT) scanning in a comparative anatomical study of the jaw musculature of 12 noctilionoid species that span all diets found within the clade. We evaluated changes in jaw muscle attachments across species, identified differences in muscle compartments, examined scaling relationships, and compared the power of diceCT and dissections to generate morphological data. We found that diceCT enables more detailed investigation of muscle compartments and generates greater PCSA values, but these are strongly correlated with estimates from dissections. Jaw muscle origin and insertion sites are relatively conserved across noctilionoids when compared to other species-rich and ecologically-diverse mammalian groups. However, we found interspecific differences in the degree of separation of the m. masseter, and in the scaling relationships of different jaw muscles with body mass, both of which might be associated with diet and feeding behavior specialization. Our study highlights an unexplored diversity in the compartmentalization and fiber architecture of bat jaw muscles. Anat Rec, 301:267–278, 2018. © 2018 Wiley Periodicals, Inc.