My major research interests focus on the mechanisms and evolution of animal movement. I am particularly interested in how muscles work in natural behaviors. Muscles are versatile motors. They can pull against each other and against their tendons in complex ways. They can act as accelerators or brakes, and their tendons can act as springs that recycle energy. These mechanisms can also interact in ways that enhance strength and reduce cost.
Muscle-tendon networks
In one series of projects, I have been studying how the complex muscle-tendon networks of snakes are used to produce and control movements that differ in speed, strength, and duration. The behaviors I have been studying include snake locomotion, constriction, and swallowing. See some of the animals and their behaviors here (opens in new window).
Snakes are uniquely interesting models for this kind of integrative research. Their simplified body form constrains their movements to bending and twisting, but their complex musculature supports a diversity movements and behaviors. For example, snakes use at least five distinct kinds of locomotion , as well as a variety of prey capture and feeding movements, such as striking, constriction , and swallowing . These behaviors require different speeds, strengths, and ranges of motion, but are all produced by the axial muscles and skeleton.
Snake epaxial muscle-tendon networks are among the longest multi-joint muscle systems known. The complex interconnections and large cross-sectional areas suggest that the epaxial muscles are major axial flexors. These muscles mainly produce broad bends in long segments of the body, but they are also active in sharper bending during constriction. In behaviors that involve undulatory movements, the long muscle-tendon networks pull on each other and on vertebral joints in complex ways that appear to enhance strength and reduce energy use. These kinds of results from diverse behaviors can illustrate both mechanisms and constraints, and thus they help us understand major principles in animal function.
This research was featured in the Biomechanics column in Natural History magazine in November 2000.
High-performance muscles
Some of my current research addresses the relationships among muscle anatomy,
mechanics, and energetics in high performance muscles. Rattlesnake tailshaker
muscle is a great system for studying these things because it is specialized for sustaining extremely high frequency contractions (up to 100 Hz!) without fatigue. This muscle system can help us understand how muscles save energy by using mechanical tradeoffs among contraction force, duration, frequency, and displacement. An offshoot of this project involved studying how metabolic capacity and contractile performance change during growth in western diamondback rattlesnakes (Crotalus atrox). Another related project currently addresses how muscles vary in capacity and performance in snakes that vibrate their tails at different frequencies. See some of the animals and their tails here (opens in new window).
Some of this research was recently featured in the In this Issue column by Kathryn Phillips in the Journal of Experimental Biology.
Small shrimp, big journey (picture to come...)
My research is not just restricted to vertebrates. With Ray Bauer and Jim Delahoussaye, I am studying the migration of juvenile Ohio shrimp (Macrobrachium ohione) up the Atchafalaya River every fall. These incredible little shrimp hatch in brackish marshes on the Louisiana coast and swim upstream by the millions as far as they can go. We’re studying how they do that. Historically, they used to make it from the Gulf Coast to the Ohio River, which pretty remarkable for such shrimpy (inch-long) shrimp! Stay tuned for more about this project in the near future.
Jumping slugs!
For a while, I also studied jumping in slugs. Yes, there are such things as jumping slugs, although I've only been able to make them flip-flop rather than actually jump. I hope to continue this project and document them in flight via slow-speed video recordings.
Meet some of our study animals here (opens in new window).
Laboratory facilities
In general, my lab is set up for the following kinds of research:
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Updated August 2007