M. E. DeMont and J. M. Gosline. (1988).
Mechanics of jet propulsion in the hydromedusan jellyfish, Polyorchis
penicillatus. I. Mechanical properties of the locomotor structure.
J. Exp. Biol. 134: 331-332.
A non-destructive test was developed to measure the static mechanical
properties of the locomotor structure (bell) in the hydromedusan jellyfish,
Polyorchis penicillatus (Eschscholtz, 1829). A nonlinear
stress-strain relationship was found, and the mean
static structural stiffness of the bell was 150 Pa. Visualization
procedures that showed the natural changes in the geometry of the deformation
of the bell were used to calculate the static modulus of elasticity of the
mesoglea, and gave a modulus of 400 Pa. Dynamic measurements on isolated
samples of mesoglea gave a mean storage modulus of 1000 Pa. The
resilience of the material was about 58%. These data were integrated to
imply that the dynamic structural stiffness of the bell is at least 400
Pa. Attempts to measure the dynamic structural stiffness directly
indicate that the dynamic stiffness of the intact bell lies between 400 and
1000 Pa. All, or most, of the potential energy stored in the mesoglea
during contractions of the bell is stored as strain energy in the radial
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
May 30, 1996