Researchers discover biological hydraulic system in tuna fins
(PHYSorg.com Biology)

Cutting through the ocean like a jet through the sky, giant bluefin tuna are built for performance, endurance and speed. Just as the fastest planes have carefully positioned wings and tail flaps to ensure precision maneuverability and fuel economy, bluefin tuna need the utmost control over their propulsive and stabilizing structures as they speed through the ocean. The outstanding maneuverability and precision locomotion of these powerful fish are supported by a vascular specialization that is unique among vertebrates, according to new research from Stanford University and the Monterey Bay Aquarium: pressurized hydraulic fin control.