November 24, 2010

Study Claims Flexible Scales Help Sharks Hunt

Researchers from the University of South Florida and the University of Alabama have discovered one reason why sharks are such great hunters--flexible scales that allow them to change direction without having to slow down.

During a presentation at the annual American Physical Society's Division of Fluid Dynamics (DFD) conference in California on Tuesday, Alabama researcher Amy Lang illustrated how the scales help control water flow separation throughout a shark's body, allowing it to turn without needing to reduce its velocity.

The scales of the shortfin mako, which resemble small teeth covering the shark's body, are wider at the tops of the scales than where they attach to the skin. According to a press release, the researchers found that the tapered design of the scales enable them "to be easily manipulated to angles of 60 degrees or more, endowing them with movement called 'denticle bristling.'"

"In nature, if you look at surfaces of animals, you'll see that they are not smooth," Lang said in a statement. "They have patterns. Why? One common application of patterning a surface is to control flow--think of the dimples of a golf ball that help the ball fly farther. We believe scales on fast-swimming sharks serve a similar purpose of flow separation control."

"As we investigate further, we imagine applications of controlling flow separation in design of aircraft, helicopters, wind turbines--anywhere flow separation is an issue," she added.

The study was sponsored in part by the National Science Foundation (NSF). In addition to Lang, Philip Motta and Maria Habegger of the University of South Florida, Emily Jones of the University of Alabama, and Robert Hueter of the Mote Marine Laboratory are credited as authors of the study, which was presented at 4:10 PM local time on November 23.


Image 1: This is a shortfin mako. Credit: P. Motta/Univ. South Florida

Image 2: This image is of the mako scales from a sample on the side of the shark. The scales in the foreground have been manually bristled and measure approximately 0.2 mm in length. Credit: P. Motta/Univ. South Florida


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