Crabs grow when their legs are broken. Crabs have the ability to regenerate broken limbs. The fundamental reason is that the information of this function exists in the DNA of crabs. When the crab is in danger, it instinctively causes some meristem cells on the fracture to divide, differentiate and grow, and gradually grows new limbs. It usually takes 45 days-100 days to grow a new limb.

After the crab's foot is broken, a soft nodule will grow on the surface of the stump in about 6 days, which is wrapped in a transparent chitin capsule and called limb bud. In the later stage, limb buds grow rapidly and begin to be segmented, and at the same time, their epithelial tissues, striated muscle fibers, motor and sensory neurons appear one after another, and then enter a slow growth stage, which lasts for several months. Finally, when it approaches molting, limb buds begin to grow rapidly again. The growth of joints between joints is completed, sensory hairs and thorns appear on the surface, sensory nerves are embedded in sensory hairs, and tissue growth is completed here. After molting, the limb buds shed chitin sacs and form new feet.

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