An octopus has hundreds of suckers that give the animal a powerful grip, but the suckers are also used to smell and taste as explained in an episode of the KQED series Deep Look. This helps the octopus identify food as it moves around.
Those hundreds of powerful suckers on octopus arms do more than just stick. They actually smell and taste. This contributes to a massive amount of information for the octopus’s brain to process, so the octopus depends on its eight arms for help.