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

First published online June 6, 2005
Journal of Experimental Biology 208, 2377-2387 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01618

This Article Figures Only Full Text Full Text (PDF) 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 Donley, J. M. Articles by Gemballa, S. Search for Related Content PubMed PubMed Citation Articles by Donley, J. M. Articles by Gemballa, S.

Patterns of red muscle strain/activation and body kinematics during steady swimming in a lamnid shark, the shortfin mako (Isurus oxyrinchus)

Jeanine M. Donley^1,*, Robert E. Shadwick¹, Chugey A. Sepulveda², Peter Konstantinidis³ and Sven Gemballa³

¹ Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093-0202, USA
² Pfleger Institute of Environmental Research, Oceanside, CA 92054, USA
³ Department of Zoology, University of Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany

^* Author for correspondence (e-mail: jdonley{at}ucsd.edu)

Accepted 29 March 2005

The dynamics of steady swimming were examined in the shortfin mako (Isurus oxyrinchus), a member of the cartilaginous fish family Lamnidae, a family known for their morphological adaptations for high-performance locomotion and their similarity in hydromechanical design to tunas. Patterns of red muscle (RM) strain (i.e. relative length change) and activation were quantified at two axial positions (0.4 and 0.6L, where L is total body length), using sonomicrometry and electromyography (EMG), and correlated with simultaneous measurements of dorsal midline kinematics during steady swimming (0.5–1 L s^–1). RM strain varied longitudinally with strain amplitudes ranging from 5.5±1.1% (S.E.M.) in the anterior to 8.7±0.9% in the posterior. We found no significant longitudinal variation in patterns of RM activation, with mean onset of activation occurring at 83–84° (90° is peak length) and offset at 200–210° at both body positions. Likewise, duty cycles were similar: 35.5±1.0% in the anterior and 32.2±1.6% in the posterior. Comparison of the timing of waves of dorsal midline curvature and predicted strain relative to measured RM strain revealed a phase shift between RM shortening and local body bending. Furthermore, when the body is bent passively, RM shortens synchronously with the surrounding white muscle (WM) and skin, as expected. During active swimming, peaks in RM strain were delayed relative to peaks in WM strain by a mean of 10% of the tailbeat cycle, with one individual as high as 17% in the anterior and nearly 50% in the posterior. The longitudinal consistency in the EMG/strain phase relationship in the mako is similar to that in the leopard shark, suggesting a consistent trend among sharks using different locomotor modes. However, unlike in the leopard shark, RM shortening in the mako is physically uncoupled from deformation of the surrounding body during steady swimming, a characteristic shared between the mako and tunas.

Key words: muscle activation, strain, swimming, lamnid, Isurus

This article has been cited by other articles:

				R. E. Shadwick and D. A. Syme Thunniform swimming: muscle dynamics and mechanical power production of aerobic fibres in yellowfin tuna (Thunnus albacares) J. Exp. Biol., May 15, 2008; 211(10): 1603 - 1611. [Abstract] [Full Text] [PDF]

				J. M. Donley, R. E. Shadwick, C. A. Sepulveda, and D. A. Syme Thermal dependence of contractile properties of the aerobic locomotor muscle in the leopard shark and shortfin mako shark J. Exp. Biol., April 1, 2007; 210(7): 1194 - 1203. [Abstract] [Full Text] [PDF]

				C. A. Sepulveda, N. C. Wegner, D. Bernal, and J. B. Graham The red muscle morphology of the thresher sharks (family Alopiidae) J. Exp. Biol., November 15, 2005; 208(22): 4255 - 4261. [Abstract] [Full Text] [PDF]