cyclopticgaze

The Big Picture

     My graduate research focuses on biomechanics and the neural control of locomotion. Ok . . . so what does that mean?

      Well, "biomechanics" is the application of physics to biological systems.  How much weight can the skeleton bear?  How do hummingbirds move their wings during hovering vs. during normal flight?  If some mathematical models tell us that honey bees can't fly, then how are they doing it?  These are biomechanical questions.

     The nervous system tells the body how to move, including how to "get around", or locomote.  But understanding how the nervous system itself behaves can only tell us so much;  the body must work within the physical constraints of its own geometry and it must also interact with its surrounding environment.  Therefore, biomechanics and neurobiology are two scientific fields that are easily married.  My research essentially asks:  How do the instructions from the nervous system get turned into meaningful movement?

Skeletons without Bones

     The field of biomechanics is greatly dominated by studies of the "traditional" musculoskeletal systems of humans and other vertebrates with bony skeletons.  These studies are of great import, yet virtually all of them share a common musculoskeletal model:  bones modeled as rigid bodies, joints modeled with defined degrees of freedom, muscles modeled as actuators.  Invertebrates are often studied for their simplicity, yet many invertebrate systems do not stray from these model constraints (e.g.: arthropods).

     But the evolutionary progenitors of all animals were soft-bodied -- animals without rigid structures for articulation, yet capable of directed, meanigful locomotion nonetheless.  To this end, my current project studies the locomotion of a soft-bodied animal with a relatively simple locomotory repertoire.

     That's not to say that these animals don't have skeletons, though.  Lots of soft-bodied animals utilize a hydrostatic skeleton.  They create stiff structures by wrapping non-compressible fluid that resists compression in tissue that resists tension.  Think of a water ballon:  put enough pressure inside (without popping it) and the ballon is stiff.  So, while these soft-bodied animals don't have rigid bones, they utilize hydrostatic pressure to stiffen up parts of their bodies.

Sea Slugs are Fun!

     My research focuses on smimming in the pteropod mollusk Clione limacina, commonly called the "sea angel".  Pteropod mollusks as a group are known as "sea butterflies" because they have wing-like structures that they flap to swim through the water.  From a physiological standpoint, mollusks are useful model organisms because of their relative simplicity.  Clione limacina specifically is an interesting species for studying locomotion and locomotory speed changes because it demonstrates two highly distinct swimming speeds. Clione is planktonic, but it is also negatively bouyant.  To keep from sinking, Clione constantly flaps its wings.  This "treading water" or "hovering" behavior is a slow swimming (~2 Hz wingbeat frequency) that the animal demonstrates tonically.  When feeding or when escaping predation, Clione enters fast swimming (~4-6 Hz).  My work examines the biomechanical and neural correlates of this distinct locomotory change.