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First published online June 11, 2007
Journal of Experimental Biology 210, 2181-2191 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.001842

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Kinematics, hydrodynamics and energetic advantages of burst-and-coast swimming of koi carps (Cyprinus carpio koi)

Guanhao Wu^1,*, Yan Yang² and Lijiang Zeng¹

¹ State Key Laboratory of Precision Measurement Technology and Instruments, Department of Precision Instruments, Tsinghua University, Beijing 100084, China
² The Laboratory for Biomechanics of Animal Locomotion, Graduate University of Chinese Academy of Sciences, Beijing 100049, China/Department of Mechanics and Mechanical Engineering, University of Science and Technology of China, Hefei 230026, China

View larger version (32K): [in this window] [in a new window]   Fig. 1. (A) Schematic drawing of the video tracking and recording setup. A white paper sheet (WP) covering the tank that is illuminated by a halogen lamp (HL) is used to provide an even background for the high-contrast images of the carp's silhouette. The emission spectrum of the halogen lamp peaks in the red to yellow region. The flow around the carp is exposed by an expanded light sheet from a continuous wave (CW) laser. A high-speed CCD camera (HSC) fitted with an optical band-pass filter was used to catch the particle images (image in C), and another CCD camera fitted with a red glass plate was used to catch the swimming kinematics (image in B). We set up a global coordinate system with its origin coinciding with the end of the Y rail and the beginning of the X rail (the side of a rail where a motor is fastened is defined as the beginning).

View larger version (6K): [in this window] [in a new window]   Fig. 2. (A) Coordinate system and notation used to describe the kinematics and wake of the fish. The bold arrow indicates the jet flow. See List of symbols for definitions. R0 and R were estimated by plotting the profiles of the velocity components u (B) and v (C) parallel to x'' and y'', respectively.

View larger version (17K): [in this window] [in a new window]   Fig. 3. The speed, U, and lateral excursion, d, versus time, t. (A) U and d curves in bout 1. (B) U and d curves in bout 13. See List of symbols for definitions of Uf, Um and Ui.

View larger version (11K): [in this window] [in a new window]   Fig. 4. Histograms of time, distance and speed variables in the burst phase and the coast phase. All the variables, including (A) t1 and t2, (B) l1 and l2 and (C) v1 and v2, are presented independently for the two burst-and-coast swimming modes (MT and HT). The values are plotted as means ± s.d. (N=12).

View larger version (105K): [in this window] [in a new window]   Fig. 5. Flow patterns generated in bout 1. A–F show the evolvement of vorticity and flow velocity vector fields at different times.

View larger version (126K): [in this window] [in a new window]   Fig. 6. Same as in Fig. 5, but for flow patterns generated in bout 13.

View larger version (5K): [in this window] [in a new window]   Fig. 7. Estimations of drag coefficients during the coast phase of the carps. (A) and (B) are for reciprocals of measured instantaneous speeds (U) during the coast phase in bouts 1 and 13, respectively.