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2002
LSU-HHMI Summer Undergraduate Research Program |
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 Lacey
Millet (Jim H. Belanger, LSU Dept Biological Sciences)
Adaptations to load changes in the locomotor systems of
terrestrial and amphibious crabs.
We are interested in the mechanisms underlying adaptation to
load by locomotor systems. Amphibious shore crabs such as the
red clawed crab (Sesarma mederi) must routinely accommodate
load changes as they move in and out of water, where buoyancy
supports a large percentage of their weight. More terrestrial
crabs, such as fiddler crabs (Uca pugnax), are not exposed routinely
to such large load changes. By comparing the gaits of these
related animals both in and out of water, we hope to gain an
understanding of how these animals cope with the load changes
during locomotion. We study these adaptations in freely-behaving
animals. We simultaneously videotape the animals with several
cameras and use a commercially available 3-D motion analysis
system to determine the kinematics of individual legs. From
this, we get gait patterns for each animal. Fiddler crabs use
an alternating tetrapod gait when on land about 80% of the time,
having a swing phase that lasts approximately 38% of the step
cycle. Occasionally, the fiddler crabs use other less common
gaits. The fiddler crabs also use an alternating tetrapod gait
in the water, but each of the legs spend approximately 55% of
the step cycle in the swing phase. Studies on the red clawed
crab are in progress. Next, we plan to examine the postural
systems of the crabs by marking points on each segment of each
crab leg, and using the motion analysis system to determine
their limb kinematics.
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