Autotomy

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Autotomy

Autotomy (from the Greek

Greek language

Greek is an Indo-European languages native to the southern Balkan peninsula, the language of the Greek people. It forms an independent branch within Indo-European....
auto = "self-" and tomy = "severing") or self amputation is the act whereby an animal severs one or more of its own appendage

Appendage

An appendage in the broadest sense is an additional or subsidiary part existing on, or added to, something which can generally still function if the appendage has never existed or is later provided or grown, or will still perform a primary function if the appendage is removed....
s, usually as a self-defense

Self preservation

Self preservation is part of an animal's instinct that demands that the organism survives. 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, the organism that is attacked. Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of the prey....
's grasp. The lost body part may be regenerated

Regeneration (biology)

In biology, an organism is said to regenerate a lost or damaged part if the part regrows so that the original function is restored.Regenerative capacity is inversely related to complexity: in general, the more complex an animal is the less regeneration it is capable of....
later.

lass="link1" onMouseover='showByLink("m4300496",this)' onMouseout='hide("m4300496")'href="http://www.absoluteastronomy.com/topics/Gecko">Gecko

Gecko

Geckos are small to average sized lizards belonging to the family Gekkonidae which are found in warm climates throughout the world. Geckos are unique among lizards in their vocalizations, making chirping sounds in social interactions with other geckos....
s, skink

Skink

Skinks are the most diverse group of lizards. They comprise the family Scincidae which shares the superfamily or infraorder Scincomorpha with several other lizard families, including Lacertidae ....
s and other lizard

Lizard

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Autotomy (from the Greek

Greek language

Appendage

Self preservation

Predation

Regeneration (biology)

Reptiles

Gecko

Skink

Lizard

Lizards are a large and widespread group of squamate reptiles, with nearly 5,000 species, ranging across all continents except Antarctica as well as most oceanic island chains....
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 wiggle, creating a deceptive sense of continued struggle and attracting the predator's attention away from the fleeing prey animal. The animal can partially regenerate

Regeneration (biology)

In biology, an organism is said to regenerate a lost or damaged part if the part regrows so that the original function is restored.Regenerative capacity is inversely related to complexity: in general, the more complex an animal is the less regeneration it is capable of....
its tail over a period of weeks. The new section will contain cartilage

Cartilage

Cartilage is a type of dense connective tissue. It is composed of specialized cells called chondrocyte that produce a large amount of extracellular matrix composed of collagen fibers, abundant ground substance rich in proteoglycan, and elastin fibers....
rather than bone

Bone

Bones are rigid organ that form part of the endoskeleton of vertebrates. They function to move, support, and protect the various organs of the body, produce red blood cell and white blood cells and store minerals....
, and the skin

Skin

The skin is the outer covering of the body, also known as the epidermis. It is the largest organ of the integumentary system made up of multiple layers of epithelial biological tissue, and guards the underlying muscles, bones, ligaments and organ s....
will have different coloration, typically darker and with little or no pattern.

Autotomy in lizards is enabled by special zones of weakness at regular intervals in the vertebra

Vertebra

A vertebra is an individual bone in the flexible column that defines vertebrate animals. The vertebral column encases and protects the spinal cord, which runs from the base of the cranium down the dorsal side of the animal until reaching the pelvis....
e below 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 a structure, usually 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....
to minimize bleeding.

Invertebrates

Other animals, such as octopuses, crab

Crab

Crabs are Decapoda 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 Ophiuroidea, are echinoderms, closely related to sea stars. They crawl across the seafloor using their flexible arms for locomotion....
s, lobster

Lobster

Clawed lobsters compose a family of large marine crustaceans. Lobsters are economically important as seafood, forming the basis of a global industry that nets United States dollar1.8 billion in trade annually....
s and spider

Spider

Spiders are air-breathing chelicerate arthropods that have eight legs, and chelicerae modified into fangs that inject venom. In their bodies the usual arthropod segments are fused into two Tagma , the cephalothorax and abdomen, joined by a small, cylindrical pedicel....
s, can also lose and regenerate appendages when necessary for survival. Autotomy occurs in some kinds of octopus for survival and for reproduction: the specialised reproductive arm (the hectocotylus

Hectocotylus

A hectocotylus is one of the cephalopod arms of the male of most kinds of cephalopods that is modified in various ways to effect the fertilization of the female's eggs....
) 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 dorsum body wall which covers the visceral mass.In many, but by no means all, species of molluscs, the Epidermis of the mantle secretes calcium carbonate and conchiolin, and creates a mollusc shell....
cavity.

Species of slugs in the genus Prophysaon
Prophysaon

Prophysaon, common name taildropper slugs, is a genus of air-breathing land slugs, terrestrial animal pulmonate gastropod mollusks in the family Arionidae, the roundback slugs....
can self-amputate a portion of their tail.

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 ejection of the internal organs of sea cucumber

Sea cucumber

Holothuroidea is a class of marine animals with an elongated body and leathery skin, which is found on the sea floor worldwide. Many holothurian species and genera, informally known as sea cucumbers, are targeted for human consumption....
s when stressed, is also a form of autotomy, and they regenerate the organ(s) lost.

Bees: a special case

The sting of various honey bee

Honey bee

Honey bees are a subset of bees, primarily distinguished by the production and storage of honey and the construction of wiktionary:perennial, Colony nests out of beeswax....
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.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 any of a variety of poisons used by certain types of animals. Generally, venom is injected by such means as 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 yellowjacket

Yellowjacket

Yellowjacket or yellow-jacket is the common name in North America for predatory wasps of the genus Vespula and Dolichovespula. Members of these genera are known simply as "wasps" in other English language countries....
wasps 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. Male honey bees develop when the queen bee lays unfertilized Egg s....
) 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.

Autotomy

Reptiles

Invertebrates

Bees: a special case

See also