It needs a shell because its' mission in life is partly to keep their abdomens protected. They cannot get punctured or else it will die. If you see a crab with no shell, you shouldn't be handling it, for it will stress it out. You shouls fill a cup about a quarter full with water, then but the crab and the right size shell in the cup and it should go into the shell. Don't leave the crab in the cup after in its shell and don't leave the crab unattended.
