Why do crabs walk sideways?

Why do crabs walk sideways?

• Answer:

  Crabs run or move sideways because that is the way their legs bend. Crabs do not have ball-and-socket joints; many crabs have joints in their legs moving in a restricted number of planes so that they can only move sideways. Many crabs like the "Shore Crab" need to scamper sideways to avoid the legs getting tangled up with each other. Muscles work in pairs. A muscle can only retract, or pull; to lengthen again it must relax and be pulled back by another 'antagonistic' muscle. The muscle blocks in crabs are attached to the inner surface of the exoskeleton, including the ten tubular legs, including the legs with claws, or chelae, as well as other appendages. Aslo,For animals, their body lengths are normally larger than the widths. For locomotion, animals usually move along the long axis of their bodies. As crabs run sideways, they are moving along the long axis of their bodies. Crabs are scavengers; they do not need to move forward in pursuit of preys like predators do.