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Recently, I have become interested in how the two
most posterior thoracic legs communicate with the
more anterior walking legs to control shell position.
One pair lifts the shell; the other stabilizes it in the
pitch plane. Two kinds of mechanisms might be
important in this control: signals from mechanoreceptors
in the shell support legs, and signals, (efference
copy), from the two pairs of walking. Since little
is known about walking in hermit crabs, I must first
understand how the walking legs operate. I have
been recording walking leg movement during locomotion
with a video camera, and recording emgs
from selected muscles. At the same time, I have constructed
a computer model of walking leg and shell
support movements that enables me to calculate
forces and joint torques under different experimental
conditions. Using this I will determine whether
local proprioceptive reflexes, signals from walking
leg motor centers, or both, control the action of the
two posterior thoracic appendages. I believe that by
understanding how signals between motor centers
and sensory feedback are used in this simple system,
it will be easier to understand similar processes in
more complex animals.
I received my B.A. from Harvard, and then studied
the comparative physiology of movement at Stanford
University, receiving my Ph.D. in 1965. I came to
the University of Connecticut in 1966 after post-doctoral
training at Cambridge and Bristol Universities in
England.
Selected Publications
Chapple, W.D. (1993). Dynamics of reflex co-contraction in
hermit crab abdomen: experiments and a systems model.
J.Neurophysiol. 69, 1904-1917.
Chapple, W.D. (1997). Regulation of muscle stiffness during
periodic length changes in the isolated abdomen of the hermit
crab. J.Neurophysiol. 78, 1491-1503.
Chapple, W.D. (2002). Mechanoreceptors innervating soft
cuticle in the abdomen of the hermit crab, Pagurus pollicarus.
J. Comp. Physiol. A. 188,753-766.
Chapple, W.D. and J.L. Krans. (2004) Cuticular receptor
activation of postural motoneurons in the abdomen of the
hermit crab, Pagurus pollicarus. J. Comp. Physiol. A. 190, 365-
377.
Krans, J.L. and W.D. Chapple. (2005) The action of spike
frequency adaptation in the postural motoneurons of hermit
crab abdomen during the first phase of reflex activation. J.
Comp. Physiol. A. 191, 157-174.
Krans, J.L. and W.D. Chapple. (2005) Variability of motoneuron
activation and the modulation of force production in a postural
reflex of the hermit crab abdomen. J. Comp. Physiol. A. 191,
761-775.