An integrated approach towards characterising the functional mechanics and energetics of insect fight muscles

昆虫是地球上最具多样性和经济重要性的动物类别，毫无疑问，它们取得巨大成功的原因之一是它们令人难以置信的飞行能力，在机动性和控制方面通常远远超过脊椎动物。在人类眨眼的时间里，绿头苍蝇可以拍打翅膀50次，使用许多微小的肌肉来驱动和控制每一次翅膀拍打-有些肌肉细如人类的头发。与飞行的脊椎动物不同，昆虫的翅膀没有肌肉;相反，它们都隐藏在胸腔内。了解昆虫如何有效地满足飞行的高能量需求，使用它们非常复杂的飞行马达，因此提出了一个令人兴奋的挑战，生物学家和工程师都感兴趣。在肌肉中，通常存在力产生和速度之间的权衡，这给昆虫飞行带来了问题。有些昆虫已经进化出肌肉，每次收缩都不需要神经元激活。这些力量肌肉可以在高频率下工作（在一些蚊子中高达1000 Hz），同时仍然产生很大的力量，因为大部分肌肉可以由收缩装置组成。然而，结果是，这些力量肌肉无法产生快速变化的力量生产，必要的机动飞行。相反，无数的小转向肌肉负责产生机翼运动的快速变化。尽管如此，这些操纵肌肉也必须在高频率下工作，同时处理由更大的动力肌肉产生的高功率输出。这项资助的目的是使用一种综合的方法来获得迄今为止对昆虫飞行肌肉的力学，功能和能量学的最详细的了解。我们将根据不同的飞行肌肉在飞行中的作用，确定它们的运动、神经刺激、力量产生和效率如何变化。我们将比较双翅目（苍蝇）物种和其他昆虫目的肌肉，以进一步了解自然选择如何塑造具有不同空中行为和生态的物种的飞行马达。目前不可能同时测量昆虫的所有上述参数，主要是由于尺寸限制。相反，我们将使用一种组合的方法来分别测量每一个，然后联合收割机的信息给肌肉功能的详细图片。我们使用时间分辨显微断层扫描，最近开发的技术，使之成为可能，第一次，可视化和测量内部结构的运动活的，飞行的昆虫和电生理学记录体内肌肉动作电位。我们还记录了翅膀的运动，使我们能够通过匹配翼拍参数来整理实验数据，然后将这些数据应用于相同肌肉的体外工作循环研究，以便可以模拟它们的长度变化和神经元激活，就像它们在体内一样。这将使我们能够确定肌肉如何利用诸如转向肌肉中的负功和动力肌肉中的弹性储存等机制来提高效率和性能。我们还将通过测量风洞中系留飞行过程中氧气消耗和二氧化碳产生的速率，确定肌肉的能量消耗如何影响飞行和飞行机动的总能量成本。使用这样一种综合方法，我们将对昆虫飞行的控制和能量学的功能机制提供独特的见解。这项研究将对那些对自然选择如何改变适应不同目的的肌肉功能感兴趣的生物学家感兴趣。这些输出还将为工程师设计扑翼式无人驾驶航空系统提供灵感，这些系统通常受到低效电机的限制。

Insects are the most diverse and economically important classes of animals on earth and there is little doubt that one of the reasons for their great success is their incredible flying ability, which typically far surpasses that of vertebrates in terms of manoeuvrability and control. In the time that it takes a human to blink, a blowfly can beat its wings 50 times, powering and controlling each wingbeat using numerous tiny muscles - some as thin as a human hair. Unlike their flying verterbrate counterparts, insect wings contain no muscles; instead they are all hidden inside the thorax. Understanding how insects efficiently meet the high-energy demands of flight, using their remarkably complex flight motor therefore presents an exciting challenge that is of interest to both biologists and engineers.In muscles there is typically a trade-off between force production and speed, which presents a problem for insect flight. Some insect orders they have evolved power muscles that do not require neuronal activation for each contraction. These power muscles can operate at high frequencies (up to 1000 Hz in some mosquitoes), while still producing high forces as the majority of the muscle can consist of contractile apparatus. However, a consequence is that these power muscles are unable to produce rapid changes in their force production, necessary for manoeuvring flight. Instead, a myriad of small steering muscles are responsible for producing rapid changes in wing motion. Nonetheless, these steering muscles must also operate at high frequencies, while simultaneously dealing with the high power output produced by the much larger power muscles.The aim of this grant is to use an integrated approach to gain the most detailed understanding of the mechanics, function and energetics of insect flight muscle to date. We will determine how the movements, neural stiumulation, force production and efficiency of different flight muscles changes according to their role in the flight. We will compare muscles across dipteran (flies) species and other insect orders to further understand how natural selection has shaped the flight motor in species with different aerial behaviour and ecologies.Measuring all of the above parameters simultaneously in insects is currently impossible, largely due to size limitations. Instead we will use a combination of methods to measure each separately and then combine the information to give a detailed picture of muscle function. We use time-resolved microtomography, a recently developed technique that makes it possible, for the first time, to visualise and measure the movements of the internal structures inside a live, flying insect and electrophysiology to record in vivo muscle action potential. We also record wing movements allowing us to collate data across experiments by matching wingbeat parameters.These data will then be applied to in vitro work loop studies of the same muscles so that their length changes and neuronal activation can be simulated as if they were in vivo. This will allow us to determine how the muscles make use of mechanisms such as negative work in the steering muscles and elastic storage in the power muscles to increase efficiency and performance. We will also determine how the muscle's energy consumption contributes to the overall energetic cost of flight and flight manoeuvres, by measuring the rates of oxygen consumption and carbon dioxide production during tethered flight in a wind tunnel.Using an integrated approach such as this we will provide a unique insight into the functional mechanisms underlying the control and energetics of insect flight. This research will be of interest to biologists interested in how natural selection alters the function of muscles adapted for different purposes. The outputs will also provide engineers inspiration for the design of flapping unmanned air systems that are typically limited by inefficient motors.