Crab a **** has 10 legs which is strictly speaking , but as a child I memorized Xunzi's "Persuasion": "Crab six knees and two chelates", also sang the crab children's song: "Crab a ah claw eight, the two ends of the tip of the so big one". So in most people's impression, the crab is six feet plus two chelae.

But crabs are a class of decapods, and normal crabs have a pair of pincer-like feet for digging holes, defense, and offense, called chelicerae. And the remaining four pairs of feet are used for walking or paddling and are called stepping feet. The chelipeds and stomps do not have the same function.

So technically speaking, a crab should have eight legs that can walk and two chelipeds that don't have the function of walking, or ten legs.

The characteristics that all crabs have **** in common are:

1. All crabs are covered with a chitinous carapace. The shell protects the crab's body, and young crabs need to grow bigger and bigger by molting their shells. The new shells are soft and collapsible after molting, but the new shells usually harden within 12 hours. This is one of the reasons why crabs are classified in the class Mollusca.

2. All crabs belong to the order Decapoda under the order Mollusca. That is, two pincers are added to the crab's legs in addition to the stepping foot when counting the legs.

3. All crabs belong to the order Hypochondriata under Decapoda. The crab's umbilicus is like a folded up tail close to its body, and the umbilicus of a breeding female crab carries fertilized eggs. Because of this feature, all crabs are classified as short-tailed infraspines under the order Decapoda.