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Published October 29, 2013 | Supplemental Material + Published
Journal Article Open

Passive energy recapture in jellyfish contributes to propulsive advantage over other metazoans


Gelatinous zooplankton populations are well known for their ability to take over perturbed ecosystems. The ability of these animals to outcompete and functionally replace fish that exhibit an effective visual predatory mode is counterintuitive because jellyfish are described as inefficient swimmers that must rely on direct contact with prey to feed. We show that jellyfish exhibit a unique mechanism of passive energy recapture, which is exploited to allow them to travel 30% further each swimming cycle, thereby reducing metabolic energy demand by swimming muscles. By accounting for large interspecific differences in net metabolic rates, we demonstrate, contrary to prevailing views, that the jellyfish (Aurelia aurita) is one of the most energetically efficient propulsors on the planet, exhibiting a cost of transport (joules per kilogram per meter) lower than other metazoans. We estimate that reduced metabolic demand by passive energy recapture improves the cost of transport by 48%, allowing jellyfish to achieve the large sizes required for sufficient prey encounters. Pressure calculations, using both computational fluid dynamics and a newly developed method from empirical velocity field measurements, demonstrate that this extra thrust results from positive pressure created by a vortex ring underneath the bell during the refilling phase of swimming. These results demonstrate a physical basis for the ecological success of medusan swimmers despite their simple body plan. Results from this study also have implications for bioinspired design, where low-energy propulsion is required.

Additional Information

© 2013 National Academy of Sciences. Edited by Steven Vogel, Duke University, Durham, NC, and accepted by the Editorial Board August 21, 2013 (received for review April 16, 2013) The New England Aquarium provided cultured medusae. B.J.G., J.H.C., S.P.C., C.J.S., D.T., and S.P. were supported by Multidisciplinary University Research Initiative (MURI) Grant N00014-08-1-0654 through the Office of Naval Research (ONR), and J.O.D. was supported by MURI Grant N00014-10-1-0137 through the ONR. Author contributions: B.J.G., J.H.C., and S.P.C. designed research; B.J.G. performed research; C.J.S., J.O.D., D.T., and S.P. contributed new reagents/analytic tools; B.J.G., C.J.S., and J.O.D. analyzed data; and B.J.G., J.H.C., S.P.C., and J.O.D. wrote the paper. The authors declare no conflict of interest. This article is a PNAS Direct Submission. S.V. is a guest editor invited by the Editorial Board. This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1306983110/-/DCSupplemental.

Attached Files

Published - 17904.full.pdf

Supplemental Material - pnas.201306983SI.pdf

Supplemental Material - sm01.avi

Supplemental Material - sm02.avi


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