Structural and functional scaling of the respiratory system of flying beetles

动物生物学中一个明显的规律是，昆虫和其他节肢动物通常比脊椎动物小。为什么会这样？3亿多年前，在古生代晚期，比现在活着的昆虫大10倍的巨型昆虫在地球上游荡。地质学家最近的发现表明，当时大气中的氧气含量比现在高得多（31%比21%）。这些发现表明，由于它们向组织输送氧气的方式，今天的昆虫很小（而在古生代是巨大的）。这个项目通过使用水果金龟子来验证这个假设，金龟子是当今世界上最大的甲虫。将进行生理和成像实验，以确定较大的昆虫是否将其身体的更大一部分投入到呼吸结构中，并经历相关的负面后果（或权衡），例如大脑或消化道的比例缩小。一种新开发的神经刺激系统将用于评估高要求飞行期间的呼吸功能。3D x射线断层扫描和共聚焦显微镜将用于测量呼吸系统、大脑、消化道和肌肉的体积和结构。利用这些技术，该项目将测试较大的甲虫是否必须缩小其重要器官（如大脑）的大小和功能，以便向其组织输送氧气？受氧气输送限制的假说。因此，这个项目有可能解释动物生物学中最广泛的模式之一。了解动物设计的这些物理限制对于开发利用生物激励流体系统的工程微注射系统的新技术以及了解大气变化对动物的潜在影响至关重要。该研究项目还将包括教育和培训部分，包括开发基于网络的K-12教学资源，以及针对研究生、本科生和高中生的研究培训。

One obvious pattern in animal biology is that insects and other arthropods are generally smaller than vertebrates. Why is this? More than 300 million years ago, in the late Paleozoic, giant insects up to 10-fold larger than those alive today roamed the earth. Recent findings from geologists have shown that the atmosphere had substantially more oxygen than today (31% vs. 21% today). These findings suggest that insects are small today (and were giant in the Paleozoic) because of the way they delivery oxygen to their tissues. This project tests this hypothesis by using fruit chafer beetles, the largest beetles living in the world today. Physiological and imaging experiments will be conducted to determine whether larger insects invest a greater fraction of their body as respiratory structure, and experience associated negative consequences (or trade-offs) such as reduced proportional sizes of the brain or digestive tract. A newly developed neural stimulating system will be used to assess respiratory function during the high demands of flight. 3D x-ray tomography and confocal microscopy will be used to measure the volume and structure of the respiratory system, brain, digestive tract, and muscles. Using such technologies, this project will test whether larger beetles must reduce the size and function of essential organs (such as the brain) in order to deliver oxygen to their tissues ? the limited by oxygen delivery hypothesis. Thus, this project has the potential to explain one of the most broad-scale patterns in animal biology. Understanding such physical limits on animal design is critical for development of new technologies for engineering micro-injection systems that utilize bio-inspired fluidic systems, and for understanding the potential effects of atmospheric changes on animals. This research project will also include educational and training components, including development of a web-based K-12 teaching resource, and research training for graduate, undergraduate, and high school students.