Atmospheric Oxygen Influences on the Size of Modern and Fossil Insects.

大气中的氧气对现代和化石昆虫大小的影响最近的地质模型表明，在过去的5亿年里，氧气水平发生了很大的变化。大气中氧气的这些变化被用来解释大量的进化事件，包括大灭绝、动物多样性的变化和动物对土地的征服（Berner， VandenBrooks和Ward， 2007）。这种氧气变化最常被引用和最引人注目的影响之一是，古生代氧气水平的增加使得脊椎动物和昆虫的体型增大。然而，高氧导致昆虫巨人症的有趣假设被两个主要问题削弱了：1)缺乏统计证据表明，在这些氧气波动时期存在的动物群体中，体型与氧气水平相关；2)缺乏现代生理学研究来支持这一假设。因此，PI将从多方面研究氧气对昆虫发育和进化的影响。他将测量从石炭纪到三叠纪博物馆中化石最丰富的三个主要昆虫化石群的体型。现代蜻蜓的祖先？现代蟑螂和古翼虫的祖先？一个灭绝的群体]，并对这一时期昆虫的平均或最大尺寸是否与氧气相关进行了首次统计分析。随后，他将从这些古老的分类群中培养出两个物种，跨越过去发生的氧气范围——蜻蜓Anax junius和蟑螂blatiella germanica ？为了更好地理解不同的氧气对现代生理的影响。PI还将尝试开发有史以来第一个古氧气水平的代用物：化石昆虫的腿气管直径与腿长之比。最近在阿贡国家实验室使用相衬x射线同步加速器成像技术进行的研究表明，昆虫腿的气管直径取决于两个因素：身体大小和大气含氧量。PI将尝试可视化保存在琥珀中的昆虫化石的腿部气管，然后使用在不同氧气水平下饲养的现代蟑螂的腿部气管直径与腿长之比来预测昆虫化石生活时的大气氧气浓度。开发一种评估地质大气氧含量的独立技术将是地质学和气候科学的重大进步，并有助于解决目前相互竞争的模型。昆虫巨人症引起了公众的广泛兴趣，并成为吸引他们学习古生物学、进化和生理学基本过程的焦点。PI将利用这种兴趣，通过与亚利桑那州立大学ask - a - biology网站（http://askabiologist.asu.edu/）和亚利桑那科学中心合作，突出古生物学和进化方面正在进行的研究，以生产新的K-12教学资源。PI目前正在与博物馆密切合作，开发第一个关于过去和现在气候变化的展览。他计划将这项关于昆虫巨人症的研究纳入一个展览，让所有年龄的博物馆观众都感兴趣。

ATMOSPHERIC OXYGEN INFLUENCES ON THE SIZE OF MODERN AND FOSSIL INSECTS (0746352)Jon Harrison, PIRecent geological models have suggested that oxygen levels varied significantly over the past 500 million years. These variations in atmospheric oxygen have been invoked to explain a vast array of evolutionary events, including major extinctions, changes in animal diversity, and the conquest of land by animals (reviewed by Berner, VandenBrooks and Ward, 2007). One of the most oft-cited and dramatic proposed effects of this oxygen variation is that increased oxygen levels during the Paleozoic allowed for increases in body size of vertebrates and insects. However, the intriguing hypothesis that hyperoxia was responsible for insect gigantism is weakened by two major problems: 1) the lack of statistical evidence that body size correlates with oxygen levels in the groups of animals that were present during these times of oxygen fluctuation and 2) a lack of modern physiological studies to support this hypothesis. Therefore, the PI will carry out a multi-faceted approach to the question of the impact of oxygen on insect development and evolution. He will measure body sizes of the three major fossil insect groups for which museum fossils are most abundant from the Carboniferous period through the Triassic period [Odonatoptera ? ancestors of modern dragonflies, Blattodea ? ancestors of modern cockroaches, and Palaeodictyopterida ? an extinct group], and perform the first statistical analysis of whether average or maximal insect size correlates with oxygen across this period. He will subsequently rear two species descended from these ancient taxa across the range of oxygen that occurred in the past - the dragonfly Anax junius, and the cockroach, Blatella germanica ? to better understand the effect of varying oxygen on modern physiology. The PI also will attempt to develop the first ever proxy for paleo-oxygen levels: the ratio of leg tracheal diameter to leg length in fossil insects. Recent studies using phase contrast x-ray synchrotron imaging at Argonne National Labs have shown that insect leg tracheal diameter depends on two factors: body size and atmospheric oxygen level. The PI will attempt to visualize leg tracheae in fossil insects preserved in amber, and then use the ratio of leg tracheal diameter to leg length for modern cockroaches reared in different oxygen levels to predict what the atmospheric oxygen concentration was when the fossilized insect lived. Development of an independent technique for assessing geologic atmospheric oxygen levels would be a major advance in geology and climate science and could help resolve current competing models. Insect gigantism is of broad interest to the general public, and serves as a focal point to draw them into learning about fundamental processes of paleontology, evolution and physiology. The PI will leverage this interest to highlight ongoing research in paleontology and evolution by partnering with ASU Ask-A-Biologist web site (http://askabiologist.asu.edu/) and the Arizona Science Center to produce a new K-12 teaching resource. The PI is currently working closely with museums to develop the first exhibit on past and present climate change. He plans on incorporating this research on insect gigantism into an exhibit which will be of interest to museum goers of all ages.