QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

First published online October 7, 2004
Journal of Experimental Biology 207, 3945-3958 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.01258

This Article Figures Only Full Text Full Text (PDF) Supplementary Material Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Johansson, L. C. Articles by Lauder, G. V. Search for Related Content PubMed PubMed Citation Articles by Johansson, L. C. Articles by Lauder, G. V.

Hydrodynamics of surface swimming in leopard frogs (Rana pipiens)

L. Christoffer Johansson^1,* and George V. Lauder²

¹ Dept of Theoretical Ecology, Lund University, Ecology Building, SE-223 62 Lund, Sweden
² Dept of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA

^* Author for correspondence (e-mail: christoffer.johansson{at}teorekol.lu.se)

Accepted 23 August 2004

The kinematics of swimming frogs have been studied extensively in the past and, based on these results, hypotheses regarding the hydrodynamics of frog swimming can be generated. To test these hypotheses we used digital particle image velocimetry (DPIV) to quantify the flow structure of the wake produced by the feet during the propulsion phase of the kick of surface swimming frogs (Rana pipiens). These frogs use two different gaits, asynchronous and synchronous kicking, and the magnitude of the thrust produced by the feet differs between asynchronous (34±5.4 mN foot^–1) and synchronous kicking (71±13.3 mN foot^–1), as does maximum swimming speed, with higher swimming speed and forces produced during the synchronous kicks. Previous studies have suggested that an interaction between the feet, resulting in a single posteriorly directed fluid jet, as the feet come together at the end of synchronous kicks, may augment force production. Our results show, however, that each foot produces its own distinct vortex ring, in both asynchronous and synchronous kicking of the feet. There is no evidence of a central jet being produced even during powerful synchronous kicks (maximum thrust calculated was 264 mN foot^–1). An alternative mechanism of force production could be the lift-based paddling recently suggested for delta-shaped feet of swimming birds. However, the orientation of the vortex rings generated by the feet is almost perpendicular to the swimming direction for both gaits and there is only a slight asynchrony of the shedding of the distal (start) and proximal (stop) vortex rings, which is different from what would be expected by a dominantly lift-based mechanism. Thus, our results do not support lift as a major mechanism contributing to thrust. Instead, our data support the hypothesis that propulsion is based on drag and acceleration reaction forces where the thrust is generated by separated, but attached, vortex rings on the suction side of the feet, resulting in vortices that are shed behind the frogs during both asynchronous and synchronous kicking.

Key words: frog, Rana pipiens, anuran, amphibian, DPIV, digital particle image velocimetry, paddling, kicking, swimming, locomotion, kinematics, hydrodynamics, vortex ring, limb, foot

This article has been cited by other articles:

				C. T. Richards The kinematic determinants of anuran swimming performance: an inverse and forward dynamics approach J. Exp. Biol., October 1, 2008; 211(19): 3181 - 3194. [Abstract] [Full Text] [PDF]

				J. Peng and J. O. Dabiri An overview of a Lagrangian method for analysis of animal wake dynamics J. Exp. Biol., January 15, 2008; 211(2): 280 - 287. [Abstract] [Full Text] [PDF]

				C. T. Richards and A. A. Biewener Modulation of in vivo muscle power output during swimming in the African clawed frog (Xenopus laevis) J. Exp. Biol., September 15, 2007; 210(18): 3147 - 3159. [Abstract] [Full Text] [PDF]

				B. W. Tobalske and K. P. Dial Aerodynamics of wing-assisted incline running in birds J. Exp. Biol., May 15, 2007; 210(10): 1742 - 1751. [Abstract] [Full Text] [PDF]

				J. Peng, J. O. Dabiri, P. G. Madden, and G. V. Lauder Non-invasive measurement of instantaneous forces during aquatic locomotion: a case study of the bluegill sunfish pectoral fin J. Exp. Biol., February 15, 2007; 210(4): 685 - 698. [Abstract] [Full Text] [PDF]