Ever wondered why crabs don't walk forward? Here is why...
To make it easy to bury themselves into sand or even squeeze into narrow spaces, they are made with a wide, flattened shape. With their shape it restricts movement at the 'shoulder' joints of their legs. It is actually possible for a crab to shuffle forward, but only slowly. By flexing the second joint of their legs they can move much faster. Their joints are like a humans knees, simple hinges, difference is they move sideways.
Some crab species do move forward
Now you know that a crab can move forward, they just choose not to.
For a video of why crabs move forward click here.
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