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Updated: Jun 2, 2026
05:12
Swimming Performance Assessment in Fishes
Published on: May 20, 2011
Red muscle function in stiff-bodied swimmers: there and almost back again.
Douglas A Syme1, Robert E Shadwick
1Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada. syme@ucalgary.ca
Summary
Endothermic red muscles in fish do not guarantee thunniform swimming. Muscle function and swimming mechanics in thresher sharks show varied benefits based on body size, challenging evolutionary links.
Area of Science:
- * Comparative biomechanics
- * Fish locomotion
- * Evolutionary physiology
Background:
- * Tunas and lamnid sharks exhibit stiff-bodied, thunniform swimming linked to internalized, endothermic red muscles.
- * This muscle specialization is anteriorly located, with unique architecture limiting undulation to the tail.
Purpose of the Study:
- * To investigate if endothermic red muscles necessitate thunniform swimming.
- * To analyze muscle function and swimming mechanics in the common thresher shark (Alopias vulpinus).
- * To explore the evolutionary relationship between red muscle specialization and swimming modes.
Main Methods:
- * Review of locomotor systems in lamnids and tunas.
- * In vivo muscle function analysis in thresher sharks.
- * Swimming mechanics assessment in thresher sharks.
Main Results:
- * Common thresher sharks display swimming mechanics not strictly conforming to the thunniform model.
- * The presence of endothermic, internalized red muscles does not solely predict thunniform swimming.
- * Observed benefits of specialized red muscle vary significantly with fish body size.
Conclusions:
- * Endothermic red muscle specialization is not a strict predictor of thunniform swimming.
- * The functional advantages of this muscle type are context-dependent, particularly influenced by body size.
- * Thunniform swimming may not be solely evolutionarily tied to red muscle specialization.
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