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

大气作为氧气（O2）的来源，为所有依靠氧气来促进新陈代谢的生物提供能量。今天，大气中的氧气含量约为21%，然而在过去的5.5亿年里，氧气含量可能上升到30-35%，也可能下降到12%。地质学家早就认识到，大气中氧气的大规模波动会对当代生物的生理产生重大影响，并假设古代大气的变化导致了重大的行为、生理和生态适应。这项合作研究将重建古代大气中的氧气条件，以研究慢性缺氧（低氧）和高氧（高氧）对美洲鳄胚胎发育、生理功能和骨骼系统的影响。短吻鳄是大型脊椎动物始祖目的“冷血”代表，始祖目还包括恐龙和鸟类。祖龙起源于大气含氧量丰富的晚二叠纪（约2.8亿年前），经历了大气含氧量不足的晚三叠纪（约22亿年前）。尽管大气中氧气的波动很大，短吻鳄显然还是存活了下来（并且茁壮成长）。这将是首次在长期暴露于不同氧水平的胚胎后脊椎动物中进行此类研究，这些动物从事各种自然行为（休息，自愿和强迫活动，从运动中恢复，消化，禁食）。鳄鱼卵将在六种处理下孵化：缺氧（12%和16%），常氧（21%）和高氧（25%，30%和35%）。记录发育过程、孵化时间、孵化成功率和全胚代谢率。孵化后，一些短吻鳄会在与孵化期间相同的条件下继续生长。其他的将在不同的处理之间转移，以确定胚胎的氧气环境是否（以及如何）限制了孵化的幼崽的解剖和生理。该合作项目将汇集三个不同科学重点的实验室-全动物生理学，骨组织学和分子生物学-并将拓宽我们对生理，解剖和生化过程如何相互作用的理解，以确定整体有机体性能。该项目将培训本科生、研究生和博士后，并提供一个框架，在这个框架内，从环境对有机体形式和功能的影响角度分析系统，并将研究成果置于发展和/或进化轨迹中。这个项目的结果将通过改进鳄鱼养殖方法找到直接的工业应用，我们的实验产生的丰富数据和组织样本将通过加州大学欧文分校的鳄鱼组织库与其他研究人员共享。最后，该项目将包括对K-12学生和他们的老师的强有力的外展组成部分，主要来自南加州高少数民族和低社会经济地区的学校。该项目的综合性质将使我们能够设计基于探究的演示和教育模块，使用从实验中产生的原始数据，解决几个生命和地球科学教育内容标准。

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.