Autotomy or 'self-amputation', is the behaviour whereby an animal sheds or discards one or more of its own appendages, usually as a self-defense mechanism to elude a predator's grasp or to distract the predator and thereby allow escape. Some animals have the ability to regenerate the lost body part later. Autotomy has multiple evolutionary origins and is thought to have evolved at least nine times independently in animals. The term was coined in 1883 by Leon Fredericq.
A white-headed dwarf gecko with tail lost due to autotomy
A lizard tail shed by autotomy
The conspicuous change in the tail pattern of this marbled gecko indicates regeneration after autotomy.
A fishing spider with two limbs missing
Regeneration in biology is the process of renewal, restoration, and tissue growth that makes genomes, cells, organisms, and ecosystems resilient to natural fluctuations or events that cause disturbance or damage. Every species is capable of regeneration, from bacteria to humans. Regeneration can either be complete where the new tissue is the same as the lost tissue, or incomplete after which the necrotic tissue becomes fibrotic.
Sunflower sea star regenerates its arms.
Dwarf yellow-headed gecko with regenerating tail
Axolotls can regenerate a variety of structures, including their limbs.
Spiny mice (Acomys cahirinus pictured here) can regenerate skin, cartilage, nerves and muscle.