|
| |
|
|
|
|
||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | ||||
Journal of Experimental Biology, Vol 199, Issue 10 2139-2151, Copyright © 1996 by Company of Biologists
JOURNAL ARTICLES |
J Long, M Hale, M Mchenry and M Westneat
The functions of fish skin during swimming remain enigmatic. Does skin stiffen the body and alter the propagation of the axial undulatory wave? To address this question, we measured the skin's in situ flexural stiffness and in vivo mechanical role in the longnose gar Lepisosteus osseus. To measure flexural stiffness, dead gar were gripped and bent in a device that measured applied bending moment (N m) and the resulting midline curvature (m-1). From these values, the flexural stiffness of the body (EI in N m2) was calculated before and after sequential alterations of skin structure. Cutting of the dermis between two caudal scale rows significantly reduced the flexural stiffness of the body and increased the neutral zone of curvature, a region of bending without detectable stiffness. Neither bending property was significantly altered by the removal of a caudal scale row. These alterations in skin structure were also made in live gar and the kinematics of steady swimming was measured before and after each treatment. Cutting of the dermis between two caudal scale rows, performed under anesthesia, changed the swimming kinematics of the fish: tailbeat frequency (Hz) and propulsive wave speed (body lengths per second, L s-1) decreased, while the depth (in L) of the trailing edge of the tail increased. The decreases in tailbeat frequency and wave speed are consistent with predictions of the theory of forced, harmonic vibrations; wave speed, if equated with resonance frequency, is proportional to the square root of a structure's stiffness. While it did not significantly reduce the body's flexural stiffness, surgical removal of a caudal scale row resulted in increased tailbeat amplitude and the relative total hydrodynamic power. In an attempt to understand the specific function of the scale row, we propose a model in which a scale row resists medio-lateral force applied by a single myomere, thus functioning to enhance mechanical advantage for bending. Finally, surgical removal of a precaudal scale row did not significantly alter any of the kinematic variables. This lack of effect is associated with a lower midline curvature of the precaudal region during swimming compared with that of the caudal region. Overall, these results demonstrate a causal relationship between skin, the passive flexural stiffness it imparts to the body and the influence of body stiffness on the undulatory wave speed and cycle frequency at which gar choose to swim.
This article has been cited by other articles:
|
|
 |
|
  A. M. Horner and B. C. Jayne The effects of viscosity on the axial motor pattern and kinematics of the African lungfish (Protopterus annectens) during lateral undulatory swimming J. Exp. Biol., May 15, 2008; 211(10): 1612 - 1622. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. E. Shadwick FOUNDATIONS OF ANIMAL HYDRAULICS: GEODESIC FIBRES CONTROL THE SHAPE OF SOFT BODIED ANIMALS J. Exp. Biol., February 1, 2008; 211(3): 289 - 291. [Full Text] [PDF]
|
|
|
|
 |
|
 D. A. KELLY Penises as Variable-Volume Hydrostatic Skeletons Ann. N.Y. Acad. Sci., April 1, 2007; 1101(1): 453 - 463. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. H. Long Jr, T. J. Koob, K. Irving, K. Combie, V. Engel, N. Livingston, A. Lammert, and J. Schumacher Biomimetic evolutionary analysis: testing the adaptive value of vertebrate tail stiffness in autonomous swimming robots J. Exp. Biol., December 1, 2006; 209(23): 4732 - 4746. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. L. Brainerd and E. Azizi Muscle fiber angle, segment bulging and architectural gear ratio in segmented musculature J. Exp. Biol., September 1, 2005; 208(17): 3249 - 3261. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. Rivera, A. H. Savitzky, and J. A. Hinkley Mechanical properties of the integument of the common gartersnake, Thamnophis sirtalis (Serpentes: Colubridae) J. Exp. Biol., August 1, 2005; 208(15): 2913 - 2922. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. A. Ashley-Ross and B. F. Bechtel Kinematics of the transition between aquatic and terrestrial locomotion in the newt Taricha torosa J. Exp. Biol., February 1, 2004; 207(3): 461 - 474. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. J. McHenry and J. Jed The ontogenetic scaling of hydrodynamics and swimming performance in jellyfish (Aurelia aurita) J. Exp. Biol., November 15, 2003; 206(22): 4125 - 4137. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. L. Katz Design of heterothermic muscle in fish J. Exp. Biol., August 1, 2002; 205(15): 2251 - 2266. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. J. Koob and J. H. Long Jr. The Vertebrate Body Axis: Evolution and Mechanical Function Integr. Comp. Biol., February 1, 2000; 40(1): 1 - 18. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. vS. Hoff and R. J. Wassersug Tadpole Locomotion: Axial Movement and Tail Functions in a Largely Vertebraeless Vertebrate Integr. Comp. Biol., February 1, 2000; 40(1): 62 - 76. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. A. Pabst To Bend a Dolphin: Convergence of Force Transmission Designs in Cetaceans and Scombrid Fishes Integr. Comp. Biol., February 1, 2000; 40(1): 146 - 155. [Abstract] [Full Text] [PDF]
|
|
