Horseshoe crabs have 12 legs. They use 5 pairs of legs for walking. The sixth pair is called the chelicera and is used to move food into their mouths. Horseshoe crabs don’t have jaws, so they also use their legs to crush their food before putting it into their mouths. Horseshoe crabs eat worms, algae, clams, and other small prey they uncover in the sediment on the ocean floor.