Autotomy
Encyclopedia
Autotomy or self amputation is the act whereby an animal severs one or more of its own appendage
s, usually as a self-defense
mechanism designed to elude a predator
's grasp. The lost body part may be regenerated
later.
Gecko
s, skink
s, and other lizard
s, and some salamander
s that are captured by the tail will shed part of the tail structure and thus be able to flee. The detached tail will continue to wriggle, creating a deceptive sense of continued struggle and distracting the predator's attention from the fleeing prey animal. The animal can partially regenerate
its tail over a period of weeks. The new section will contain cartilage
rather than bone
, and the skin
may be distinctly discolored compared to the rest of the body. The technical term for this ability to drop the tail is caudal autotomy.
Autotomy in lizards is enabled by special zones of weakness at regular intervals in the vertebrae posterior to the vent. Essentially, the lizard contracts a muscle to fracture a vertebra rather than break the tail between two vertebrae. Sphincter
muscles in the tail then contract around the caudal artery
to minimize bleeding.
Other animals, such as octopuses, crab
s, brittle star
s, lobster
s and spider
s, can also lose and regenerate appendages when necessary for survival. Autotomy occurs in some kinds of octopus for survival and for reproduction: the specialized reproductive arm (the hectocotylus
) detaches from the male during mating and remains within the female's mantle
cavity.
Autotomic stone crabs
are used as a self-replenishing source of food by humans, particularly in Florida. Harvesting is accomplished by removing one or both claws from the live animal and returning it to the ocean where it can regrow the lost limb(s).
Species of (land) slugs in the genus Prophysaon
can self-amputate a portion of their tail. There is known autotomy of the tail of sea snail Oxynoe panamensis
under persistent mechanical irritation.
Evisceration
, the ejection of the internal organs of sea cucumbers when stressed, is also a form of autotomy, and they regenerate the organ(s) lost.
Some sea slugs exhibit autotomy. Both Discodoris lilacina
and Berthella martensi will often drop their entire mantle skirt when handled, leading to Discodoris lilacina
also being called Discodoris fragilis. The members of Phyllodesmium
will drop a large number of their cerata
each, on the tip having a large sticky gland that secretes a sticky substance.
species is a different case; the sting apparatus is modified in such a way that it tears cleanly away from the bee's body, and has its own ganglion
that keeps the musculature of the sting shafts moving (thus embedding the sting deeper) and the venom
sac pumping for several minutes after it detaches. Unlike most cases of autotomy, the bee dies shortly afterwards (they do not grow a new sting apparatus). All species of true honey bees (genus Apis) have this form of autotomy. No other stinging insect, including the yellowjacket
wasp and the Mexican honey wasp, have the sting apparatus modified this way, though they may have barbed stings. The sting of a queen honey bee has no barbs, however, and does not autotomize. Further, the genitalia of male honey bees (drones
) also autotomize during copulation, and form a mating plug
, which must be removed by the genitalia of subsequent drones if they are also to mate with the same queen. The drones die within minutes of mating.
Appendage
In invertebrate biology, an appendage is an external body part, or natural prolongation, that protrudes from an organism's body . It is a general term that covers any of the homologous body parts that may extend from a body segment...
s, usually as a self-defense
Self preservation
Self-preservation is behavior that ensures the survival of an organism. It is universal among living organisms. In some vertebrates, pain and fear are parts of this mechanism. Pain causes discomfort so that the organism is inclined to stop the pain...
mechanism designed to elude a predator
Predation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
's grasp. The lost body part may be regenerated
Regeneration (biology)
In biology, regeneration is the process of renewal, restoration, and growth that makes genomes, cells, organs, organisms, and ecosystems resilient to natural fluctuations or events that cause disturbance or damage. Every species is capable of regeneration, from bacteria to humans. At its most...
later.
Reptiles and salamanders
Gecko
Geckos are lizards belonging to the infraorder Gekkota, found in warm climates throughout the world. They range from 1.6 cm to 60 cm....
s, skink
Skink
Skinks are lizards belonging to the family Scincidae. Together with several other lizard families, including Lacertidae , they comprise the superfamily or infraorder Scincomorpha...
s, and other lizard
Lizard
Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...
s, and some salamander
Salamander
Salamander is a common name of approximately 500 species of amphibians. They are typically characterized by a superficially lizard-like appearance, with their slender bodies, short noses, and long tails. All known fossils and extinct species fall under the order Caudata, while sometimes the extant...
s that are captured by the tail will shed part of the tail structure and thus be able to flee. The detached tail will continue to wriggle, creating a deceptive sense of continued struggle and distracting the predator's attention from the fleeing prey animal. The animal can partially regenerate
Regeneration (biology)
In biology, regeneration is the process of renewal, restoration, and growth that makes genomes, cells, organs, organisms, and ecosystems resilient to natural fluctuations or events that cause disturbance or damage. Every species is capable of regeneration, from bacteria to humans. At its most...
its tail over a period of weeks. The new section will contain cartilage
Cartilage
Cartilage is a flexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes and the intervertebral discs...
rather than bone
Bone
Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...
, and the skin
Skin
-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...
may be distinctly discolored compared to the rest of the body. The technical term for this ability to drop the tail is caudal autotomy.
Autotomy in lizards is enabled by special zones of weakness at regular intervals in the vertebrae posterior to the vent. Essentially, the lizard contracts a muscle to fracture a vertebra rather than break the tail between two vertebrae. Sphincter
Sphincter
A sphincter is an anatomical structure, or a circular muscle, that normally maintains constriction of a natural body passage or orifice and which relaxes as required by normal physiological functioning...
muscles in the tail then contract around the caudal artery
Caudal artery
The Caudal artery is the portion of the dorsal aorta of a vertebrate that passes into the tail.It is analogous to the median sacral artery in man.-External links:*...
to minimize bleeding.
Invertebrates
Crab
True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...
s, brittle star
Brittle star
Brittle stars or ophiuroids are echinoderms in the class Ophiuroidea closely related to starfish. They crawl across the seafloor using their flexible arms for locomotion. The ophiuroids generally have five long slender, whip-like arms which may reach up to in length on the largest specimens...
s, lobster
Lobster
Clawed lobsters comprise a family of large marine crustaceans. Highly prized as seafood, lobsters are economically important, and are often one of the most profitable commodities in coastal areas they populate.Though several groups of crustaceans are known as lobsters, the clawed lobsters are most...
s and spider
Spider
Spiders are air-breathing arthropods that have eight legs, and chelicerae with fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other groups of organisms...
s, can also lose and regenerate appendages when necessary for survival. Autotomy occurs in some kinds of octopus for survival and for reproduction: the specialized reproductive arm (the hectocotylus
Hectocotylus
A hectocotylus is one of the arms of the male of most kinds of cephalopods that is modified in various ways to effect the fertilization of the female's eggs. It is a specialized, extended muscular hydrostat used to store spermatophores, the male gametophore...
) detaches from the male during mating and remains within the female's mantle
Mantle (mollusc)
The mantle is a significant part of the anatomy of molluscs: it is the dorsal body wall which covers the visceral mass and usually protrudes in the form of flaps well beyond the visceral mass itself.In many, but by no means all, species of molluscs, the epidermis of the mantle secretes...
cavity.
Autotomic stone crabs
Florida stone crab
The Florida stone crab, Menippe mercenaria, is a crab found in the western North Atlantic, from Connecticut to Belize, including Texas, the Gulf of Mexico, Cuba and the Bahamas that is widely caught for food.-Description:...
are used as a self-replenishing source of food by humans, particularly in Florida. Harvesting is accomplished by removing one or both claws from the live animal and returning it to the ocean where it can regrow the lost limb(s).
Species of (land) slugs in the genus Prophysaon
Prophysaon
Prophysaon, common name taildropper slugs, is a genus of air-breathing land slugs, terrestrial pulmonate gastropod mollusks in the family Arionidae, the roundback slugs.These slugs can self-amputate a portion of their tail...
can self-amputate a portion of their tail. There is known autotomy of the tail of sea snail Oxynoe panamensis
Oxynoe panamensis
Oxynoe panamensis is a species of small sea snail or sea slug, a bubble snail, a marine gastropod mollusk in the family Oxynoidae.-Distribution:Oxynoe panamensis is found in mangrove swamps along the Baja, California and Mexico coasts....
under persistent mechanical irritation.
Evisceration
Evisceration (autotomy)
Evisceration is a method of autotomy involving the ejection of internal organs used by animals as a defensive strategy.*Sea cucumbers eject parts of the gut in order to scare predators. The gut can then be regenerated in a few days by cells in the interior of the sea cucumber....
, the ejection of the internal organs of sea cucumbers when stressed, is also a form of autotomy, and they regenerate the organ(s) lost.
Some sea slugs exhibit autotomy. Both Discodoris lilacina
Discodoris lilacina
Discodoris lilacina is a species of sea slug, a dorid nudibranch, shell-less marine gastropod mollusks in the family Discodorididae....
and Berthella martensi will often drop their entire mantle skirt when handled, leading to Discodoris lilacina
Discodoris lilacina
Discodoris lilacina is a species of sea slug, a dorid nudibranch, shell-less marine gastropod mollusks in the family Discodorididae....
also being called Discodoris fragilis. The members of Phyllodesmium
Phyllodesmium
Phyllodesmium is a genus of predatory sea slugs, aeolid nudibranchs, marine gastropod mollusks in the family Facelinidae. These nudibranchs occur in the tropical Indo-Pacific Oceans....
will drop a large number of their cerata
Cerata
Cerata are anatomical structures found in nudibranch sea slugs, marine opisthobranch gastropod mollusks.They are dorsal and lateral outgrowths on the upper surfaces of the body....
each, on the tip having a large sticky gland that secretes a sticky substance.
Bees
The sting of various honey beeHoney bee
Honey bees are a subset of bees in the genus Apis, primarily distinguished by the production and storage of honey and the construction of perennial, colonial nests out of wax. Honey bees are the only extant members of the tribe Apini, all in the genus Apis...
species is a different case; the sting apparatus is modified in such a way that it tears cleanly away from the bee's body, and has its own ganglion
Ganglion
In anatomy, a ganglion is a biological tissue mass, most commonly a mass of nerve cell bodies. Cells found in a ganglion are called ganglion cells, though this term is also sometimes used to refer specifically to retinal ganglion cells....
that keeps the musculature of the sting shafts moving (thus embedding the sting deeper) and the venom
Venom
Venom is the general term referring to any variety of toxins used by certain types of animals that inject it into their victims by the means of a bite or a sting...
sac pumping for several minutes after it detaches. Unlike most cases of autotomy, the bee dies shortly afterwards (they do not grow a new sting apparatus). All species of true honey bees (genus Apis) have this form of autotomy. No other stinging insect, including the yellowjacket
Yellowjacket
Yellowjacket is the common name in North America for predatory wasps of the genera Vespula and Dolichovespula. Members of these genera are known simply as "wasps" in other English-speaking countries...
wasp and the Mexican honey wasp, have the sting apparatus modified this way, though they may have barbed stings. The sting of a queen honey bee has no barbs, however, and does not autotomize. Further, the genitalia of male honey bees (drones
Drone (bee)
Drones are male honey bees. They develop from eggs that have not been fertilized, and they cannot sting, since the worker bee's stinger is a modified ovipositor .-Etymology:...
) also autotomize during copulation, and form a mating plug
Mating plug
right|thumbnail|A mating plug in a female [[Richardson's ground squirrel]] A mating plug, also known as a copulation plug, sperm plug, vaginal plug, or sphragis, is gelatinous secretion used in the mating of some species. It is deposited by a male into a female genital tract and later hardens into...
, which must be removed by the genitalia of subsequent drones if they are also to mate with the same queen. The drones die within minutes of mating.
See also
- Antipredator adaptation
- Self-amputation
- AinhumAinhumAinhum is a painful constriction of the base of the fifth toe frequently followed by bilateral spontaneous amputation a few years later. The disease occurs predominantly in black Africans and their descendants...
- AutoamputationAutoamputationAutoamputation is the spontaneous detachment of an appendage from the body. This is not to be confused with self-amputation....
Further reading
- Pekarinen E. (1994). "Autotomy in arionid and limacid slugs". Journal of Molluscan Studies 60(1): 19-23. Abstract
- autotomy in sea gastropod