Meeting Abstract
Bluefin tuna are trans-oceanic migrators known for their efficient locomotion. They possess a range of physiological and mechanical adaptations geared towards high-performance swimming. We equipped Atlantic bluefin tuna with motion-sensitive tags and video cameras to quantify the gaits and kinematics of wild fish. Our data reveal significant variety in tuna swimming kinematics, ranging from continuous locomotion to two types of intermittent locomotion. The tuna carrying these tags sustained swimming speeds in excess of 3 m s-1 (1.2 body lengths s-1), while beating their tail at a frequency of 0.9 Hz. Some descents were entirely composed of passive glides, with slower descents featuring more gliding, while ascents were primarily composed of active tail-beats. While the locomotive advantages of the tuna’s fusiform body shape and endothermy are well established, the contributions of their unique musculoskeletal geometry are less clear. The aerobic red muscle that powers swimming is positioned medially, with more of the musculature positioned anteriorly than posteriorly. The red muscle is connected to the spine through a network of long tendons and bony ribs. We provide new musculoskeletal architecture measurements of tuna red muscle, tendon, ribs, and spine, enabled by a novel dissection approach. We developed a two-dimensional musculoskeletal model and kinematic simulation of sustained swimming to assess effects of tendon stretch on muscle fiber dynamics. We hypothesize that stretch of the elastic tendons allows the muscle fibers to be activated at their optimal lengths and lower shortening velocities. Quantitative understanding of the tuna biomechanics could inform the design of bioinspired vehicles. Supported by ONR.
