Why (not how) do crabs walk sideways??

Question

To the intellectual w.w.w. audience. Why aren't they 'forward-marching' like anything else in the animal kingdom? (something they know about the future that we don't, perhaps ??)

Answer 1

they walk side-ways so that they dont have to fight the ocean current or waves

Answer 2

If you look at the structure of the legs you'll see that the articulations are really levered to have power in a single dimension. There's basically a series of muscles in line that contract the sections of the leg in a particular dimension.

Contrast this to your arms - think of the shoulder. The deltoid muscle attaches to the side of the humerus and to the very end of the clavicle, allowing motion of your arm up, in the same plane as the body. The pectoral muscles attact at the chest and on the anterior surface of the head of the humerus, pulling the arm toward the front. You've also got muscles attaching in other areas that allow three dimensions of freedom of motion.

Muscles moving your legs are similarly arranged allowing large range of motion.

Poor crab just has these legs shooting radially out from the body with muscles that have most force pulling inward to the body. If you analyze the vectors of force they will end up pulling from one side, hence the motion of the animal. There aren't any strong attachments to allow forward/backward motion of a leg.

Answer 3

It has to do with their leg joints. They aren't made for the crabs legs to bend back and forth, which would promote forward and reverse movement. They are bend side to side, which promotes sideways movement.

Answer 4

im a crab fisherman all i know is they move the fastest that way

Answer 5

they dont want to turn their backs on the gay crabs

Answer 6

why do we walk forwards and not sideways? hum?