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Wake dynamics and locomotor function in fishes: interpreting evolutionary patterns in pectoral fin design
Eliot G Drucker1, George V Lauder
1Museum of Comparative Zoology, Harvard University, 26 Oxford St., Cambridge, Massachusetts 02138.
Integrative and Comparative Biology
|June 18, 2011
Summary
The pectoral fins of bluegill sunfish generate stronger turning and braking forces than rainbow trout, demonstrating the hydrodynamic impact of evolutionary changes in ray-finned fish fin design.
Area of Science:
- Evolutionary biology
- Comparative anatomy
- Biomechanics
Background:
- Actinopterygii (ray-finned fishes) exhibit significant anatomical diversification in paired fins.
- Two major trends in pectoral fin evolution are observed: reorientation of the fin base and migration of the fin's body position.
- The functional significance of these evolutionary trends in pectoral fin design is largely untested.
Purpose of the Study:
- To investigate the influence of pectoral fin structure on fluid forces during maneuvering locomotion.
- To test the hypothesis that evolutionary changes in pectoral fin morphology impact hydrodynamic performance.
Main Methods:
- Digital particle image velocimetry (DPIV) was used for quantitative wake visualization.
- Swimming forces were measured in rainbow trout (plesiomorphic pectoral fins) and bluegill sunfish (apomorphic pectoral fins).
Main Results:
- Bluegill sunfish pectoral fins generate significantly higher forces for turning compared to rainbow trout.
- Sunfish pectoral fins produce greater direct braking forces closer to the body's center of mass than trout.
- These findings support hypotheses linking pectoral fin structure to hydrodynamic function.
Conclusions:
- Evolutionary transformations in pectoral fin morphology have significant hydrodynamic consequences.
- Pectoral fin position and orientation influence force generation crucial for maneuvering and braking in fishes.
- This study provides insight into the functional importance of major evolutionary changes in Actinopterygii pectoral fins.
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