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Published June 1, 2007 | Published + Supplemental Material
Journal Article Open

Morphological diversity of medusan lineages constrained by animal–fluid interactions


Cnidarian medusae, commonly known as jellyfish, represent the earliest known animal taxa to achieve locomotion using muscle power. Propulsion by medusae requires the force of bell contraction to generate forward thrust. However, thrust production is limited in medusae by the primitive structure of their epitheliomuscular cells. This paper demonstrates that constraints in available locomotor muscular force result in a trade-off between high-thrust swimming via jet propulsion and high-efficiency swimming via a combined jet-paddling propulsion. This trade-off is reflected in the morphological diversity of medusae, which exhibit a range of fineness ratios (i.e. the ratio between bell height and diameter) and small body size in the high-thrust regime, and low fineness ratios and large body size in the high-efficiency regime. A quantitative model of the animal–fluid interactions that dictate this trade-off is developed and validated by comparison with morphological data collected from 660 extant medusan species ranging in size from 300 µm to over 2 m. These results demonstrate a biomechanical basis linking fluid dynamics and the evolution of medusan bell morphology. We believe these to be the organising principles for muscle-driven motility in Cnidaria.

Additional Information

© 2007 The Company of Biologists Ltd. Accepted 11 March 2007. First published online May 21, 2007. The authors acknowledge support from the NSF Ocean Sciences Division – Biological Oceanography Program (OCE-0623475 awarded to J.O.D., OCE-0351398 and -0623534 awarded to S.P.C. and OCE-0350834 and -0623508 awarded to J.H.C.).

Attached Files

Published - DABjeb07.pdf

Supplemental Material - DABjeb07_movie_1.mov

Supplemental Material - DABjeb07_movie_2.mov

Supplemental Material - DABjeb07_supp_table.pdf


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