The Aerobic Dive Limit: Oxygen Transport and Depletion in Emperor Penguins

Abstract: The research will examine blood and muscle oxygen store depletion in relation to the documented aerobic dive limit (ADL, onset of post-dive blood lactate accumulation) in diving of emperor penguins. The intellectual merits of this proposal involve its evaluation of the physiological basis of the ADL concept. The ADL is probably the most commonly-used, but rarely measured, factor to interpret and model the behavior and foraging ecology of diving animals. Based on prior studies, and on recent investigations of respiratory and blood oxygen depletion during dives of emperor penguins, it is hypothesized that the ADL is a result of the depletion of myoglobin (Mb)-bound oxygen and increased glycolysis in the primary locomotory muscles. This project will accurately define the physiological mechanisms underlying the ADL through 1) evaluation of the rate and magnitude of muscle oxygen depletion during dives in relation to the previously measured ADL, 2) characterization of the hemoglobin-oxygen dissociation curve in blood of emperor penguins and comparison of that curve to those of other diving and non-diving species, 3) application of the emperor hemoglogin-oxygen dissociation curve to previously collected oxygen and hemoglobin data in order to estimate the rate and magnitude of blood oxygen depletion during dives, and 4) measurement of muscle phosphoocreatine and glycogen concentrations in order to estimate their potential contributions to muscle energy metabolism during diving. The project also continues the census and monitoring of the emperor colonies in the Ross Sea, which is especially important in light of both fisheries activity and the movement of iceberg B15-A. Broader impacts of the project include: 1) technological development of microprocessor-based, 'backpack' near-infrared spectrophotometer, which will be applicable not only to other species, but also to other fields (i.e., exercise physiology), 2) collaboration with the Department of Anesthesia at the U.S. Naval Hospital in San Diego in the training of anesthesia residents in research techniques, 3) the training and thesis research of two graduate students in these techniques and in Antarctic field research, and 4) a better understanding of the ADL concept and its use in the fields of diving behavior and physiology. In addition the annual census of emperor penguin colonies in the Ross Sea, in conjunction with the continued evaluation of previously developed remote cameras to monitor colony status, will form the basis of a new educational web site, and allow development of an educational outreach program to school children through SeaWorld of San Diego.摘要：本研究将围绕帝企鹅潜水行为中的血液与肌肉氧储备消耗，结合已记录的有氧潜水极限（aerobic dive limit，简称ADL，即潜水后血液乳酸堆积的起始时刻）展开分析。本提案的学术价值在于其对ADL概念生理学基础的验证。ADL或许是解读并建模潜水动物行为与觅食生态时应用最为广泛、却极少被实测的指标。基于既往研究以及近期针对帝企鹅潜水过程中呼吸与血液氧消耗的调查，本研究提出假说：ADL的产生源于肌红蛋白（Mb）结合氧的耗尽以及主要运动肌肉内糖酵解过程的增强。 本项目将通过以下四项工作精准阐明ADL背后的生理学机制：1）评估潜水过程中肌肉氧消耗的速率与规模，并结合此前测得的ADL开展关联分析；2）表征帝企鹅血液的血红蛋白-氧解离曲线，并将该曲线与其他潜水及非潜水物种的同类曲线进行对比；3）将帝企鹅血红蛋白-氧解离曲线应用于既往收集的氧与血红蛋白数据，以估算潜水过程中血液氧消耗的速率与规模；4）测定肌肉磷酸肌酸与糖原浓度，以评估其在潜水过程中对肌肉能量代谢的潜在贡献。 本项目还将持续对罗斯海区域的帝企鹅种群开展普查与监测——鉴于当地渔业活动与冰山B15-A的移动，该项工作尤为重要。本项目的综合拓展影响包括：1）技术开发：研制基于微处理器的“背包式”近红外分光光度计，该设备不仅可应用于其他物种研究，亦可拓展至运动生理学等其他领域；2）与美国圣地亚哥海军医院麻醉科合作，培训麻醉住院医师掌握相关研究技术；3）培养两名研究生，使其掌握相关技术并开展南极野外研究与学位论文研究；4）加深学界对ADL概念的理解，以及其在潜水行为与生理学领域的应用。 此外，罗斯海区域帝企鹅种群的年度普查，结合对已开发的用于监测种群状态的远程相机的持续评估，将为全新的教育类网站奠定基础，并可依托圣地亚哥海洋世界面向学龄儿童开发教育推广项目。