Breathing seems like one of the simplest things we do, but actually the structures and motions of the rib cage are enormously complex. Ribs and associated muscles (the intercostal muscles) contribute to breathing in humans and other animals, but the exact respiratory actions of the ribs and intercostal muscles have been controversial for centuries. Why is it so difficult to infer the actions of these muscles from their structure and attachments to the ribs? The answer lies in: (1) the 3D complexity of rib shape; (2) the 3D complexity of rib motion during breathing; (3) the 3D complexity of intercostal muscles; and (4) variation in all of the above from top to bottom and front to back of the rib cage. Decades of work on dogs and humans have finally yielded a solid understanding of exhalation and inhalation in these mammals, but the work has been slow and laborious. Now a new 3D X-ray technology, X-ray Reconstruction of Moving Morphology (XROMM), has just become available and will vastly speed up the collection of data on bone shape and bone motion in living animals. In this project, XROMM will be used to determine 3D rib shape, 3D rib motion, and intercostal muscle function in seven species: three lizards, two birds, an alligator, and a crocodile. These animals were selected because they show a diverse spectrum of rib shapes, rib joint morphologies, body forms, and locomotor behaviors (swimming, running and flying). The advent of XROMM will make it possible to add these seven new species to the current knowledge of just two species, all within just three years. In the future, the results of this work can be used to reconstruct the respiratory system of extinct animals, with particular relevance to the controversial respiratory mechanisms of dinosaurs. The project includes interdisciplinary training for a Postdoctoral Fellow and a doctoral student, contributions to K-12 education, to increasing participation of underrepresented groups, and to enhancing scientific infrastructure. The postdoc and graduate student will gain interdisciplinary training through interactions with our collaborators in Engineering, Computer Science, and the Center for Computation and Visualization. The postdoc and graduate student will take the lead on specific projects, mentor undergraduate researchers, and work with K-12 teachers from the Providence Public Schools. More than 80% of students in the Providence Public School system are from underrepresented groups and more than 80% qualify for free or reduced cost lunch. In cooperation with K-12 teachers, the scientists will develop and deliver lessons and projects to teach the students about animal motion, biomechanics, and scientific methods such as XROMM. Toward enhancing scientific infrastructure, the XROMM technology will be improved and new software developed to simplify the data analysis. All hardware and software innovations are made public and are available to colleagues (through an NSF Research Coordination Network and via The complete metadata generated by the study will be published immediately through a public online database ( Metadata publication allows colleagues to see the contents of the data sets and suggest collaborations. After publication or after 10 years, whichever is earlier, all data will be made public.

National Science Foundation (NSF)
Division of Integrative Organismal Systems (IOS)
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Steven Ellis
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Brown University
United States
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