Squid Beaks Use Chemical Trick to Keep From Tearing Off

March 27, 2008

Researchers have figured out how a jumbo squid's hard, razor-sharp beak can slice through the soft tissue of its prey—without tearing off from the stress.

The work solves a longstanding mystery over a problem akin to anchoring a knife blade in Jell-O, according to the authors of the new study.

Squid beaks are one of the hardest organic materials known. They're also powerful: With a single notch through a captured fish's back, a squid beak can sever the fish's nerve cord and cause paralysis.

(Related: "Jumbo Squid Invading Eastern Pacific" [March 30, 2007].)

But each blow sends powerful forces toward the soft tissues at the beak's base, and no one had ever managed to figure out how the beak dissipates those forces to prevent damage.

So Ali Miserez and his colleagues at the University of California, Santa Barbara, painstakingly sampled bits of beak all the way from tip to base and discovered changing ratios of chitin (a tough sugar chain), water, and proteins in a matrix that spans the length of the structure.

The beak exhibited an overall stiffness gradient that differs a hundredfold from beak tip to base. Though rigid at its cutting end, the beak gradually becomes softer and more flexible as it approached the soft muscle tissue.

The findings offer a potential solution for the longtime engineering struggle to attach mechanically mismatched materials.

"This could really revolutionize the way engineers think about attaching materials together in all sorts of applications," Frank Zok, a study co-author, said.

The paper appears in this week's issue of the journal Science.

All Organic

Miserez and his team mapped out the specific chemical composition of each section of beak and matched it to the mechanical properties at that point. (See a photo of a jumbo squid, aka Humboldt squid or red devil.)

Continued on Next Page >>




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