Meeting Abstract
Over the past century, the avian respiratory system has received considerable interest, with numerous studies describing morphological variation between and within species. While gross dissections and casts of the lower respiratory tract have permitted qualitative descriptions of variation in some avian taxa, there has not yet been a systematic quantitative analysis of these differences. Advances in imaging, such as x-ray computed microtomography (microCT), permit non-destructive visualization and quantification of pulmonary structures in situ. Six deceased African grey parrots (Psittacus erithacus erithacus) were microCT scanned, and the air sacs, lung surfaces, and airways were segmented to produce 3D surface models. These structures were qualitatively analyzed to characterize overall shape, branching pattern, and left-right symmetry. Quantitative metrics were taken from multi-planar reconstructions of the microCT scans and include: 1) distances to the ventrobronchi and dorsobronchi from the carina; 2) the area of the primary bronchus where each major secondary bronchus branches; and, 3) the area of the ostium for each of the large secondary bronchi (ventrobronchi, laterobronchi, and first four dorsobronchi). Qualitatively, the air sacs demonstrated the most intraspecific variation, with marked differences in the caudoventral extension of the cervical sacs along the internal aspect of the sternum. Additionally, quantitative metrics demonstrated reduced variability in structures more closely associated with the aerodynamic inspiratory valve. This work advances our understanding of the avian respiratory system, providing both a novel methodology and a baseline for evaluating interspecific variation in future studies.
