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Form, function, and divergence of a generic fin shape in small cetaceans
Vadim Pavlov1,2, Cecile Vincent3, Bjarni Mikkelsen4
1Hopkins Marine Station, Stanford University, Pacific Grove, CA, United States of America.
Plos One
|August 11, 2021
Summary
Cetacean fins evolved into generic wing designs for aquatic life. Their shape variations are linked to specific functions like thrust, stability, and turning, optimizing them as hydrofoils.
Area of Science:
- Evolutionary biology
- Hydrodynamics
- Comparative anatomy
Background:
- Cetacean fins (tail flukes and dorsal fin) are key adaptations for aquatic life.
- These appendages exhibit wing-like shapes for efficient lift generation and reduced drag.
Purpose of the Study:
- To test if cetacean fin cross-sections share invariant dimensionless parameters across species and body lengths (Hypothesis I).
- To investigate if fin shape variations are constrained by their function as fixed or flapping hydrofoils (Hypothesis II).
Main Methods:
- Analysis of fin morphological traits in relation to function, species, and body length.
- Computational Fluid Dynamics (CFD) software used to examine hydrodynamic characteristics of fin cross-sections.
- Comparison of cetacean fin cross-sections with engineered airfoils.
Main Results:
- Cetacean fins display a generic wing-like planform and streamlined cross-sections optimized for lift.
- Divergence in fin shape correlates with specialization for fixed or flapping hydrofoil functions.
- Dorsal fins are optimized for small angles of attack; tail flukes are stable at higher angles with gradual stall.
Conclusions:
- Cetacean fins evolved a conserved, generic wing-like design.
- Functional specialization drives divergence in fin morphology for efficient locomotion.
- These findings illuminate the evolutionary pathways of cetacean fin adaptations for diverse hydrodynamic demands.
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