M. E. DeMont and J.M. Gosline. (1988).
Mechanics of jet propulsion in the hydromedusan jellyfish, Polyorchis
penicillatus. II. Energetics of the jet cycle. J. Exp. Biol. 134:
333-345
Summary
The mechanical energy generated by the contraction of the
subumbrellar swimming muscles to power the jet cycle in the hydromedusan
jellyfish Polyorchis penicillatus (Eschscholtz, 1829) was measured.
This energy was experimentally partitioned into three
components during the contraction. The sum of these components was taken to
be the mechanical energy generated by the muscles during the jet cycle and
was between 8.9 x 10-5 and 1.4 x 10-4 per contraction. Energy from one
of these components is stored as strain energy in the mesoglea and powers the
refilling phase. The mesoglea can clearly act as an effective elastic
structure to antagonize the contraction of the swimming muscles completely,
and it may be designed to function at some optimum. The mechanical
significance of elastic energy storage systems in jet-propelled animals is
discussed, and this significance is clearly displayed in Polyorchis. The
usually long-duration action potential of the swimming muscles may be an
important component of the swimming mechanism, allowing the muscles to
store energy in an elastic structure at the end of the contraction phase
when little hydrodynamic thrust is developed. It is suggested that the
action potential of vertebrate cardiac muscle may have a similar
mechanical function.
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Edwin DeMont, Associate Professor
Biology Department, St. Francis Xavier University
P.O. Box 5000, Antigonish, Nova Scotia, B2G 2W5 Canada
Voice 902-867-5116 FAX 902-867-2389
edemont@juliet.stfx.ca -
May 30, 1996