© 1996 by The Society for Integrative and Comparative Biology
Springs in Swimming Animals1
Biological Sciences and Center for Marine Science Research, University of North Carolina at Wilmington Wilmington, North Carolina 28403
Animals can lower the metabolic cost of swimming by using appropriately tuned, elastic springs. Jet-powered invertebrates use springs that lie in functional parallel to their swimming muscles to power half the locomotor cycle. The parallel geometry constrains the spring to be non-linearly elastic; muscle power is diverted to load the spring only when swimming muscles are not capable of producing maximal hydrodynamic thrust. The springs of jellyfish and scallops are forced at or near their resonant frequency, producing large energy savings. Measuring the contribution of elastic energy storage to jet-powered locomotion has been facilitated by the relatively simple geometries of invertebrate locomotor systems. In contrast, complex musculoskeletal systems and kinematics have complicated the study of springs in swimming vertebrates. Skins, tendons and axial skeletons of some vertebrate swimmers have appropriate mechanical properties to act as springs. To date, though, there exist just a handful of studies that have investigated the mechanical behaviors of these locomotor structures in swimming vertebrates, and these data have yet to be integrated with measures of swimming power. Integrating mechanical, kinematic, hydrodynamic and metabolic data are required to understand more fully the role of elastic springs in vertebrate swimming energetics.