IMSI Research Seminar – Simon Sponberg

Title: Supra-resonance, ultra-fast muscles, and evolutionary transitions underlying the diverse flight of insects

Speaker: Prof Simon Sponberg (Georgia Tech)

Date: Fri, Nov 6, 2:30-4:00pm Pacific Time

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Abstract: Flapping flight has played a key role in the diversification and evolutionary success of insects. Yet they have evolved a variety of solutions with diverse wing shapes, movements, and underlying muscle physiology. In this talk I will discuss how the interplay between muscle physiology, biomechanics, and evolutionary history has shaped the diversity of insect flight, and how seemingly distinct physiological strategies can emerge from a common dynamical framework. Most insects fly as tiny mechanical resonators. What this means is that to reduce the extreme energetic costs of flapping flight at small scales, many insects store and return energy in their elastic exoskeletons to accelerate their wings back and forth at high speeds. I will first discuss how, despite the energetic advantages of resonance, most insects actually operate above their optimal resonant frequency because of muscular constraints and biomechanical tradeoffs for control. I will then explore how insects have evolved two distinct physiological strategies for powering this supra-resonant flight. Moths, locusts, and many other insects activate their flight muscles in synchrony with each wingstroke. In contrast, flies, beetles, and many bees generate multiple wingstrokes for each pulse of neural activation. This asynchronous strategy relies on stretch activation, a physiological property of flight muscle that allows rhythmic contractions without neural activation for every wingstroke, enabling the exceptionally high wingbeat frequencies of many small insects. Although these two strategies have long been recognized, our evolutionary reconstruction suggests that the four major clades of asynchronous fliers likely share a single evolutionary origin of asynchrony. Surprisingly, this implies that groups such as moths and butterflies secondarily lost asynchronous flight. We test this prediction in the synchronously flying hawkmoth, Manduca sexta, and find that its flight muscles retain the stretch-activated properties characteristic of asynchronous species. We then develop a unified biophysical framework showing how transitions between synchronous and asynchronous flight can arise from changes in muscle and wing dynamics. We demonstrate these principles in a flapping-wing robot capable of reproducing both flight strategies. Finally, using a physiological dynamic clamp that places isolated moth flight muscle into a mechanical virtual reality environment, we show that a simple change in muscle physiology can recover asynchronous dynamics in synchronous moth muscle. 

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Speaker Bio: Simon Sponberg is Glen Robinson Professor in Complex Systems at Georgia Tech with appointments in the schools of Physics (75%) and Biological Sciences (25%). He earned B.A.’s with highest honors in physics and biology at Lewis & Clark College and his Ph.D. in Integrative Biology from UC, Berkeley. He was an NSF postdoctoral fellow at the University of Washington in Biology and Physiology & Biophysics. He has 50 journal publications, including in Science, Nature, and PNAS. Sponberg was a Klingenstein-Simons Fellow in the Neurosciences, NSF CAREER awardee, Leedy Endowed Faculty Excellence Fellow, Hertz Fellow, and an International Society of Neuroethology Young Investigator. He leads an Air Force MURI team examining how the compact neural architectures of flying insects achieve fast perception and rapid decision-making in complex sensory environments. He also co-leads an NSF Biological Integration Institute on Movement Sciences and recently helped launch the new Institute for Neuroscience, Neurotechnology and Society at Georgia Tech. His research explores the compositional principles governing how physical and physiological systems interact to produce agile movement. 

Learn more about the Integrative Movement Sciences Institute (IMSI) at MovementScience.uci.edu