Autotomy

Definition

The voluntary shedding or detachment of a body part—typically an appendage—as a defense mechanism to escape predation. The sacrificed part may continue to move, distracting the predator while the animal flees. Autotomy occurs at pre-weakened fracture planes (autotomy planes) and is followed by wound sealing and often regeneration.

Etymology

From Greek autos (self) + tome (cutting), coined by Léon Fredericq in 1883.

Example

Many stick insects (Phasmatodea) autotomize a leg when grasped by a predator; the twitching limb holds the predator's attention while the insect drops and plays dead or escapes. Some spiders similarly shed legs to free themselves from silk or predator jaws.

Synonyms

• self-amputation

Related Terms

• autotomy plane
• fracture plane
• Regeneration
• aposematism
• Thanatosis
• predator swamping
• defensive behavior
• Ecdysis

Usage Notes

Distinguish from accidental injury or passive breakage: autotomy is an active, evolved mechanism with anatomical specializations. Not all animals that lose limbs can autotomize; true autotomy requires neural and muscular control plus subsequent wound closure. In crustaceans and arachnids, autotomy typically occurs at specific joints (coxa-trochanter in spiders, basi-ischiopodite in crabs); in insects, it often involves the femur-trochanter junction. The term is sometimes extended to tail autotomy in lizards, but in entomology it refers chiefly to appendage loss.