112 - Pulmonary Anatomy of the Zebra Finch (Taeniopygia Guttata) and Interspecific Comparison with the Ostrich (Struthio Camelus) and African Grey Parrot (Psittacus Erithacus)

Poster Board Number: 112
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Abstract Body : The zebra finch (Taeniopygia guttata) is one of the most commonly studied avian model systems in neuroscience, animal behavior, reproductive biology, ecology, evolution, physiology, and genetics. Despite broad interest in T. guttata, there lacks any substantial work on the respiratory anatomy of this taxon, which is surprising considering their focal role in understanding the biology of songbird vocalization. Here, we use micro-computed tomographic data to visualize the morphology of the respiratory system in T. guttata, its relationship with the postcranial skeleton, and compare it with two phylogenetically and ecologically disparate taxa: the large and flightless ostrich (Struthio camelus; n = 5), and the medium sized volant African grey parrot (Psittacus erithacus n = 11). Five naturally deceased T. guttata specimens were imaged, and their respiratory and skeletal systems segmented into three-dimensional (3D) surface models using the imaging software Avizo. Three of the birds were intubated, inflated, and scanned at maximum inspiratory capacity (MIC), and two at a natural end tidal volume (NETV). While the respiratory system of T. guttata follows the general anatomical bauplan previously described for passerines based on gross dissection and latex casting, our data show that it deviates in the following ways: (1) the caudal thoracic sacs are large, even in the two specimens imaged at NETV, extending past the caudal edge of the gas-exchanging lung; (2) the cervical diverticula occasionally fuse within the neural canal of the caudalmost cervical vertebrae to form small supramedullary diverticula, but these diverticula are rarely continuous with each other and are not seen in the other vertebral regions; and, (3) the postcranial skeleton demonstrates some external pneumatic features (e.g., the pneumotricipital fossa of the humerus), but lacks actual pneumatic spaces within cortical bone. Additionally, the abdominal air sacs are substantially reduced in volume in the birds imaged at NETV relative to MIC suggesting their possible reduced role relative to the caudal thoracic sacs in airflow and ventilation in this taxon. Our data also highlight the following differences in respiratory anatomy between T. guttata, S. camelus, and P. erithacus: (1) the abdominal air sacs are small and typically form a robust connection to large saccobronchi in T. guttata rather than the large patent ostium of the intrapulmonary primary bronchus as seen in both S. camelus and P. erithacus; (2) T. guttata fuses the interclavicular and cranial thoracic air sacs, while S. camelus and P. erithacus do not demonstrate this fusion; and, (3) the apneumatic postcranial skeleton of T. guttata is unlike S. camelus and P. erithacus, which both heavily pneumatize their postcranial skeletons.