Both physical and physiological modifications to the oxygen transport system promote high metabolic performance of tuna. The large surface area of the gills and thin blood-water barrier means that O2 utilization is high (30-50%) even when ram ventilation approaches 101 min-1kg-1. The heart is extremely large and generates peak blood pressures in the range of 70-100 mmHg at frequencies of 1-5 Hz. The blood O2 capacity approaches 16 ml dl-1 and a large Bohr coefficient (-0.83 to -1.17) ensures adequate loading and unloading of O2 from the well buffered blood (20.9 slykes). Tuna muscles have aerobic oxidation rates that are 3-5 times higher than in other teleosts and extremely high glycolytic capacity (150 μmol g-1 lactate generated) due to enhanced concentration of glycolytic enzymes. Gill resistance in tuna is high and may be more than 50% of total peripheral resistance so that dorsal aortic pressure is similar to that in other active fishes such as salmon or trout. An O2 delivery/demand model predicts the maximum sustained swimming speed of small yellowfin and skipjack tuna is 5.6 BL s-1 and 3.5 BL sec-1, respectively. The surplus O2 delivery capacity at lower swimming speeds allows tuna to repay large oxygen debts while swimming at 2-2.5 BL s-1. Maximum oxygen consumption (7-9 × above the standard metabolic rate) at maximum exercise is provided by approximately 2 × increases in each of heart rate, stroke volume, and arterial-venous O2 content difference. © 1994 Kluwer Academic Publishers.
CITATION STYLE
Bushnell, P. G., & Jones, D. R. (1994, July). Cardiovascular and respiratory physiology of tuna: adaptations for support of exceptionally high metabolic rates. Environmental Biology of Fishes. Kluwer Academic Publishers. https://doi.org/10.1007/BF00002519
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