Crustacean shuffle

A modified joint might have made all the difference to scurrying crabs as they diverged from their plodding lobsterlike brethren.

Comparing leg shape, size, and motion among three living crustaceans from increasingly ancient origins allowed Andrés Vidal-Gadea, at Louisiana State University in Baton Rouge, and his colleagues to get at the mechanics of crab walking: specifically, how some crustaceans changed their forward march into a sideways scuttle.