For nearly 20 years, Professor Eric Fortune has studied glass knifefish, a species of three-inch long electric fish that lives in the Amazon Basin. In his laboratory he tries to understand how their tiny brains control complex electrical behaviors. But he could not help but be intrigued by the special "ribbon fin" that knifefish use to swim back and forth. The fin oscillates at both ends, allowing the fish to move forward or backward. Biologists have long wondered why an animal would produce seemingly wasteful forces that directly oppose each other while not aiding its movement.
But in the Nov. 4-8 online edition of Proceedings of the National Academy of Sciences (PNAS), Fortune and a multi-disciplinary team of researchers report that these opposing forces are anything but wasteful. Rather, they allow animals to increase both stability and maneuverability, a feat that is often described as impossible in engineering textbooks.
"I read a Navy flight training manual that had a full page dedicated to the inherent tradeoff between stability and maneuverability, says Fortune, an associate professor of biology at NJIT. "Apparently the knifefish didn't read that manual, since the opposing forces surprisingly make the fish simultaneously more stable and more maneuverable."
When an animal or vehicle is stable, it resists changes in direction. On the other hand, if it is maneuverable, it has the ability to quickly change course. Generally, engineers assume that a system can rely on one property or the otherbut not both. Yet some animals prove an exception to the rule.
"Animals are a lot more clever with their mechanics than we often realize," said Noah Cowan, a professor of mechanical engineering at The Johns Hopkins University and the senior author of the multi-disciplinary research team. "By using just a little extra energy to control the opposing forces, animals seem to increase both stability and maneuverability when they
|Contact: Tanya Klein|
New Jersey Institute of Technology