Adv. Mater. doi:10.1002/adma.200801197 (2009)

The fearsome suckers with which the Humboldt squid (Dosidicus gigas) clutches its prey are lined with toothed rings. David Kisailus at the University of California, Riverside, Henrik Birkedal at the University of Aarhus in Denmark and their colleagues have peered into the jaws of these suckers to find out what makes them so strong.

The sucker rings have sharp teeth made from parallel tubes that are hollow near the circular base and filled at the sharp end. This channel-like structure directly affects the mechanical properties of the sucker rings, the authors say, adding extra grip and shear strength for terrorising prey.

Surprisingly, the sucker rings don't contain chitin, usually present in the shells of crustaceans. The sucker rings' major amino acids are glycine, tyrosine and histidine. The authors propose that hydrogen bonds between histidine residues give the rings their rigidity.