Collaborative Research: LiT: Effects of environmental oxygen on growth and physiological performance in the American alligator: A case study in experimental paleophysiology

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The atmosphere serves as a source of oxygen (O2) for all organisms that rely on O2 to power their metabolism. Today, the level of atmospheric O2 is approximately 21%, however over the past 550 million years O2 levels may have risen as high as 30-35% and dropped as low as 12%. Geologists have long recognized that large-scale fluctuations in atmospheric O2 would have had significant effects on the physiology of contemporary organisms and have hypothesized that changes in the ancient atmosphere resulted in significant behavioral, physiological and ecological adaptations. This collaborative research will recreate ancient atmospheric O2 conditions in order to investigate the effects of chronic hypoxia (low oxygen) and hyperoxia (high oxygen) on embryonic development, physiological function and the skeletal system of the American alligator. Alligators are a "cold blooded" representative of a large vertebrate group, Archosauria, which also includes dinosaurs and bird. Archosaurs originated in the Late Permian (ca. 280 million years ago) when the atmosphere was O2 rich and experienced the Late Triassic (circa 220 mya) when the atmosphere was O2 poor. Alligators obviously survived (and thrived) despite large-scale fluctuations in atmospheric O2. This will be the first such study in a post-embryonic vertebrate animal engaging in a wide variety of natural behaviors (rest, voluntary and forced activity, recovery from exercise, digestion, fasting) chronically exposed to different O2 levels. Alligator eggs will be incubated under six treatments: hypoxia (12 and 16%), normoxia (21%) and hyperoxia (25, 30 and 35%). Developmental progress, incubation time, hatching success and whole- embryo metabolic rate will be recorded. After hatching, some alligators will continue growing under the same conditions as during incubation. Others will be transferred between treatments, in order to determine whether (and how) the O2 environment of the embryo constrains the anatomy and physiology of the hatchling. This collaborative project will bring together three laboratories with different scientific emphases - whole-animal physiology, bone histology and molecular biology - and will broaden our understanding of how interactions of physiological, anatomical and biochemical processes are integrated to determine overall organismal performance. This project will train undergraduates, graduates and postdoctoral fellows, and provide a framework within which to analyze systems in terms of environmental influences on organismal form and function, and to place research results within developmental and/or evolutionary trajectories. Results from this project will find direct industry application by improving alligator farming methods, and the wealth of data and tissue samples generated by our experiments will be shared with other researchers via the Alligator Tissue Bank at UC Irvine. Finally, this project will include a strong outreach component to both K-12 students and their teachers, primarily from schools representing high-minority and low socioeconomic areas in Southern California. The integrative nature of the project will allow us to design inquiry-based demonstrations and educational modules, using raw data generated from experiments, which address several life and earth science educational content standards.