Meeting Abstract
90.8 Wednesday, Jan. 7 Non-invasive histological comparison of bone growth patterns among fossil and extant neonatal elephantids using synchrotron radiation X-ray microtomography CURTIN, A.J.*; MACDOWELL, A.A.; SCHAIBLE, E.G.; ROTH, V.L.; Duke Univ.; Advanced Light Source, Lawrence Berkeley National Lab.; Advanced Light Source, Lawrence Berkeley National Lab.; Duke Univ. amanda.curtin@duke.edu
How is bone growth modified in insular dwarfing? We applied X-ray microtomography as a non-invasive method for obtaining high-resolution image-"slices" of the femoral diaphyses of four neonatal elephantids: a stillborn modern African elephant (Loxodonta africana), one neonate of Mammuthus columbi, and two neonatal specimens of its close relative, the insular dwarf M. exilis. Scanning large objects at voxel size ~17 microns is non-standard, and required development of a method for splicing a series of images. The results compare favorably in level of detail with histological sectioning, but without the shrinkage, distortion, or loss of tissue inevitable with the latter. Transverse sections at midshaft for the two full-sized species and one of the dwarfs showed a concentric pattern of laminar bone units surrounding a medullary region containing coarse cancellous bone and cancellous trabeculae. A distinct change in tissue microstructure in the M. columbi and one M. exilis specimen marks the boundary between prenatal and postnatal periosteal bone deposition and shows that these two individuals survived birth. Laminae in the L. africana individual were significantly thinner and more numerous than those of either mammoth species; M. exilis differed from the larger mammoth in having fewer and slightly thinner laminae. Compared to M. columbi, M. exilis laminae were evidently laid down at a slower rate, even allowing for the scaling of gestation length with body size. Comparison of the full trajectory of growth in these animals is now facilitated by collaboration with P. Tafforeau, ESRF, Grenoble, through imaging of more and of fully-grown individuals.
