Mechanics of Movement

All animals face a single overriding constraint on their ability to produce fast movements - muscles contract slowly and over small distances. Repeatedly over evolutionary history, animals have overcome this limitation through the use of mechanical systems that decrease the duration of movement and thereby increase speed and acceleration. Many human-made mechanical systems incorporate this strategy. For example, in the crossbow, slow muscle contractions of a human arm load the bow and ultimately a latch releases the arrow. With this mechanism, the arrow accelerates and flies through the air at far greater speeds than would have been possible by simply throwing the arrow. The technical term for this process is power amplification. In animals, power amplification is achieved through a suite of structural adaptations including springs, latches, lever arms and linkages.

A major focus of our lab is the evolution of power amplification.  How do power-amplified systems evolve?  Do animals easily switch between using fast muscles and slow muscles?  Are there patterns in the underlying mechanics of elastic structures?  Our focus is currently on two systems - mantis shrimp (Stomatopoda) and trap-jaw ants (Formicidae) - which offer remarkably fast predatory systems and a fantastic diversity of weaponry across each group. We examine the evolutionary variation in three components of these systems: the morphology of predatory weapons, the variation in spring mechanics, and the kinematics of fast movements.  While most studies to date have focused on solving the intriguing biomechanics of single species, notably little is known about the evolutionary processes and patterns underlying the diversification of power amplified systems. Thus, using force sensors, high speed videography, field research and phylogenetic comparative methods, we probe the origins of these remarkable structures and the interrelationship between the basic physics underlying extremely fast movements and their fantastic radiations over macro-evolutionary timescales.

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