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Crab Claws

March 25, 2009

Bromine is what makes the tips of crab claws extra tough.


Why crab claws are extra tough…I’m Bob Hirshon and this is Science Update.

Pick up a Dungeness crab and you’ll see a translucent material on the tips of its legs. It’s the same material that physicist Robert Schofield of the University of Oregon saw on the claws of a striped shore crab he found on the beach. When he analyzed the material in his lab, he found it contained a high concentration of a heavy element called bromine. Schofield says the bromine makes the material in the claw tips ten times more fracture resistant than the rest of the shell.

SCHOFIELD (University of Oregon):
Generally an organism will trade off fracture resistance for hardness. And so this is something that is both hard and very fracture resistant.

Fracture is a big problem for small animals like crabs, ants and scorpions. So over time, they’ve evolved tough outer shells to protect against it. I’m Bob Hirshon for AAAS, the science society.