autotomies

Autotomies refer to the voluntary shedding or loss of a body part by an animal, typically as a predator-escape strategy. The phenomenon is widespread across several animal groups and involves specialized anatomical mechanisms that allow a part to break away with minimal harm to the rest of the body. In many cases, the lost part can be regenerated, at least partially, over time.

Caudal autotomy, the best-known form, occurs in many lizards and other reptiles. The tail detaches at predefined fracture planes within the tail vertebrae and surrounding tissues when grasped by a predator. The detached portion may continue to twitch briefly to distract the predator, providing the bearer a chance to flee. In many species, a new tail is later grown, though the replacement often differs in structure and composition from the original.

Autotomy also occurs in other phyla. In echinoderms such as brittle stars and starfish, arms can be shed at autonomic break points and regenerate over time. In arthropods, including certain crustaceans and spiders, limbs or antennae may detach at joints during a threat, allowing escape while the detached part may not immediately compromise survival.

Regeneration following autotomy varies among groups. Lizards typically regenerate a new tail that forms a cartilaginous rod rather than a true vertebral column; echinoderm limbs can sometimes fully restore the lost appendage; the process generally requires substantial energy and can leave individuals temporarily weakened or more vulnerable to predators and environmental stress.

Autotomy has important ecological and evolutionary implications as a defense mechanism. Its costs include energy expenditure for regeneration, potential loss of function, and increased risk during recovery. The phenomenon is a focal point in studies of regeneration, developmental biology, and biomechanics, and has inspired biomimetic approaches in engineering and robotics.