Eat. The spider crab has a hard shell and the longest front legs among crabs, hence its name for its spider-like shape. Spider crab is a type of sea crab that grows in Alaska, USA. They are called spider crabs because of their eight legs, spider-like appearance and more tentacles than regular crabs. The body is thick and round, the legs are slender, and the movement is slow. Most scavenger spider crabs have spiny carapace, sharp legs and long walking feet. This spiny spider crab is the largest crab in Europe, and there are nearly 100 different species found along the Australian coast. Although they have long claws and eight slender legs and look like spiders, they are slow and easily caught. Spider crabs have many raised balls on their shells. According to experts, this is a sea anemone that looks like a flower, but is a predator that feeds on water animals. It attaches to the spider crab shell, allowing the sea anemone and spider crab to "mutually benefit"