The shape-changing fins of fish are of great interest to engineers developing the locomotion and maneuvering capabilities of underwater and aerial systems. On page 310 of this issue, Pavlov et al. (1) find that the lymphatic circulatory system in tuna and other members of the Scombridae family of fish serves as a hydraulic system that actively changes the sweep angle of their second dorsal (back) and anal (underside) fins. This is an important finding because sweep-angle changes alter fin erectness and thereby affect the lift-force capacity of the fin. Such changes are used consistently during maneuvering and transient motion, especially for sharp turns. |
