autotomizing

Autotomy, or autotomy, is the voluntary shedding or loss of a body part at a specialized internal rupture plane, typically as an anti-predator defense. It is observed in several animal groups, including reptiles (notably some lizards and skinks), echinoderms (such as starfish and brittle stars), and various crustaceans. The released part is often followed by rapid wound sealing and healing, with some degree of regeneration in the remaining body.

Mechanisms of autotomization involve preformed fracture planes in the connective tissues at the site of detachment. Muscles around the plane contract to facilitate severing, and the detachment is arranged to minimize blood loss and injury to the animal. After shedding, the animal may continue to move or escape using the remaining body, while the detached part typically dangles briefly before becoming nonfunctional.

Regeneration after autotomy varies across taxa. In many lizards and other reptiles, the lost tail is replaced by a new structure that differs anatomically from the original (often a cartilaginous rod instead of a true vertebral column, with altered musculature and sensory components). In echinoderms such as starfish and brittle stars, damaged arms can regrow completely over time, especially with favorable conditions. Crustaceans and other arthropods may regrow limbs across molts, but the regenerated appendages can differ in size or capability from the originals.

Evolutionary and ecological considerations center on trade-offs. Autotomy can markedly improve short-term survival during predation, but it incurs costs such as impaired locomotion, reduced grasping or feeding ability, and energetic demands for regeneration. The frequency and effectiveness of autotomy depend on species, environmental context, and predator pressure.