14.2 Wednesday, Jan. 4 Cellular patterns and biomechanical consequences of bat wing development COOPER, Lisa Noelle*; JAST, John; BEHRINGER, Richard R.; CRETEKOS, Chris; RASWEILER, IV, John J.; SEARS, Karen E.; Univ. of Illinois; Univ. of Illinois; Univ. of Texas; Univ. of Idaho; SUNY Downstate Med. Ctr.; Univ. of Illinois firstname.lastname@example.org
Mammals evolved a stunning degree of phenotypic diversity in bone architecture in response to their occupation of extreme habitats. To achieve powered flight, bats altered the architecture of their long bones by reducing mineral concentrations and altering cross-sectional geometries. This study aimed to quantify differences in adult bone architecture of the short-tailed bat (Carollia) relative to terrestrial rodents (Mus, Peromyscus). By integrating microstructural analyses via nanoindentation tests with whole bone bending tests, as well as visualization of cross-sectional areas, this study offers a thorough documentation of architectural differences in limb bones of aerial and terrestrial mammals. Nanoindentation tests revealed that the metacarpals of bats are 40% as stiff and 36% as hard as that of Mus. Whole bone bending tests showed that the humerus of bats and mice are roughly equivalent in stiffness, however bat radii were more compliant. Micro-CT scans showed the humeral, femoral, and tibial cross-sectional geometries are equivalent in both groups; however, distal bones of the bat displayed 8-40% larger medullary cavities compared rodents. To determine how endochondral ossification differs between Carollia and Mus diaphyseal dimensions were measured. Results indicate that Carollia delays appositional ossification relative to Mus, but begins diaphyseal longitudinal growth earlier. At late fetal stages, Carollia rapidly elongates the diaphysis, a finding consistent with reports that most endochondral ossification occurs postnatally in bat forelimb bones. These findings further our understanding of the microstructural properties of chiropteran bone biology.