Coordination and Modulation of Motor Programs in Manduca Sexta

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The majority of our knowledge about how animals move is based on creatures that walk, fly or swim using rigid articulated bones and exoskeletons. However, animals without backbones invertebrates are the most numerous animals on the planet and nearly all are soft-bodied with hydrostatic skeletons for at least part of their life. These crawling creatures do not escape predators by running but instead use camouflage, chemical defenses and cryptic behavior. As a consequence, crawling has evolved into a highly specialized form of locomotion that allows soft bodied animals to move in complex and confined three dimensional structures such as tubes and branches. With a soft body, joints do not restrict movements. Such animals can crumple, compress and rotate body parts with virtually unlimited freedom. Such complex movements are very interesting from a neural control perspective because movement coordination by the nervous system has co evolved with these biomechanical features. The proposed study uses a caterpillar, the tobacco hornworm, Manduca sexta, as a model system to help understand the neural control of hydrostatic movements. Two specific aspects will be examined in detail: first we will determine how crawling is controlled by the central nervous system and how it interacts with peripheral structures such as muscles and cuticle; secondly, we will examine a unique aspect of caterpillar crawling, the ability to climb using curved hooks at the tips of the abdominal prolegs. This gripping is passive but very strong like Velcro hooks and can be actively released. We will determine how this gripping is controlled and how it is integrated into normal crawling.Although focused on understanding animal locomotion, these studies have potential applications in the design and control of a new type of flexible robot. Such robots could be used to navigate through pipelines or intricate structures such as blood vessels and air tubes. Finally, in examining the mechanism of proleg gripping it is possible that new adhesive materials could be developed that attach passively but can be released actively to avoid the tearing forces in conventional hook and loop fastenings.