Metamorphosis 20866 225311893 2008-07-13T01:05:32Z ClueBot 4928500 Reverting possible vandalism by [[Special:Contributions/69.49.146.245|69.49.146.245]] to version by 69.47.146.87. False positive? [[User:ClueBot/FalsePositives|Report it]]. Thanks, [[User:ClueBot]]. (438927) (Bot) <!--__NOTOC__-->{{otheruses1|the biological process}} [[Image:Dragonfly metamorphosis.jpg|thumb|right|A [[dragonfly]] in its final [[ecdysis|moult]], undergoing metamorphosis from its [[nymph (biology)|nymph]] form.]] '''Metamorphosis''' is a [[biological process]] by which an [[animal]] physically [[developmental biology|develops]] after [[birth]] or hatching, involving a conspicuous and relatively abrupt change in the animal's form or structure through cell [[cell growth#Cell reproduction|growth]] and [[cell differentiation|differentiation]]. Some [[insect]]s, [[amphibians]], [[Mollusca|mollusc]]s, [[crustacean]]s, [[cnidarian]]s, [[echinoderm]]s and [[tunicate]]s undergo metamorphosis, which is usually (but not always) accompanied by a change of [[habitat (ecology)|habitat]] or [[behaviour]]. Scientific usage of the term is exclusive, and is not applied to general aspects of [[cell growth]], including rapid [[growth spurt]]s. References to "metamorphosis" in [[mammal]]s are imprecise and only colloquial. ==Etymology== The word "metamorphosis" derives from [[Greek language|Greek]] ''μεταμόρφωσις'', "transformation, transforming"<ref>[http://www.perseus.tufts.edu/cgi-bin/ptext?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3D%2366805 Metamorphosis, Henry George Liddell, Robert Scott, ''A Greek-English Lexicon'', at Perseus]</ref>, from ''μετα-'' (''[[meta-]]''), "change" + ''μορφή'' (''morfe'') "form"<ref>[http://www.etymonline.com/index.php?search=Metamorphosis&searchmode=none Online Etymology Dictionary]</ref>. ==Insect metamorphosis== {| class="wikitable" align="right" |+'''Comparative Lengths of Metamorphosis''' ! style="background:#99dbaa;" | Species ! style="background:#99dbaa;" | Egg ! style="background:#99dbaa;" | Larva/Nymph ! style="background:#99dbaa;" | Pupa ! style="background:#99dbaa;" | Adult |} Metamorphosis usually proceeds in distinct stages, starting with [[larva]] or [[nymph (biology)|nymph]], optionally passing through [[pupa]], and ending as [[adult]]. There are two main types of metamorphosis in insects, [[hemimetabolism]] and [[holometabolism]]. [[Image:Grasshoppermetasnodgrass.svg|thumb|250px|Incomplete metamorphosis in the grasshopper with different instar nymphs]] The immature stages of a species that metamorphoses are usually called [[larva|larvae]], and in these stages may grow quite quickly. But in the complex metamorphosis of many insect species, only the first stage is called a larva and sometimes even that bears a different name; the distinction depends on the nature of the metamorphosis. An example of metamorphosis where the name is changed is that of a tadpole. When a tadpole metamorphosises, it becomes amphibeous; whereas, as a tadpole, during which time it's classification as an amphibian is arguable. In hemimetabolism, the development of larva often proceeds in repeated stages of growth and [[ecdysis]] (moulting), these stages are called [[instar]]s. The juvenile forms closely resemble adults, but are smaller and, if the adult has wings, lack wings. This process is also known as "simple", "gradual" or "incomplete" metamorphosis. The differences between juveniles in different instars are small, often just differences in body proportions and the number of segments. In holometabolism, the larvae differ markedly from the adults. Insects which undergo holometabolism pass through a larval stage, then enter an inactive state called [[pupa]], or [[chrysalis]], and finally emerge as adults. Holometabolism is also known as "complete" and "complex" metamorphosis. Whilst inside the pupa, the insect will excrete digestive juices, to destroy much of the larva's body, leaving a few cells intact. The remaining cells will begin the growth of the adult, using the nutrients from the broken down larva. This process of cell death is called [[histolysis]], and cell regrowth [[histogenesis]]. Whether the insect spends more time in its adult stage or in its juvenile form depends on the species. Notable examples are the [[mayfly]], whose non-eating, adult stage lives for one day, and the [[cicada]], whose juvenile stage live underground for 13 or 17 years. These species have incomplete metamorphosis. Typically, though not exclusively, species in which the adult form outlives the juvenile form undergo complex metamorphosis. Many observations have indicated that [[cell death]] plays a considerable role during physiological processes of multicellular organisms, particularly during [[embryogenesis]] and metamorphosis. <gallery> Image:ChristianBauer Pieris rapae caterpiller.jpg|''[[Small White|Pieris rapae]]'' [[larva]] Image:ChristianBauer Pieris rapae caterpiller2.jpg|''Pieris rapae'' [[pupa]] Image:ChristianBauer Pieris rapae cocoon.jpg|''Pieris rapae'' pupa, ready to hatch. Image:ChristianBauer Pieris rapae youngadult.jpg|A ''Pieris rapae'' [[adult]] </gallery> ===Hormonal control=== [[Insect]] growth and metamorphosis are controlled by [[hormone]]s synthesized by [[endocrine]] [[gland]]s near the front of the body. Some [[cell (biology)|cell]]s of an insect's [[brain]] secrete a hormone that activates [[Thorax|thoracic]] glands, which secrete a second hormone, usually [[Ecdysone]] (a [[steroid]]), that induces metamorphosis. Moreover, the [[corpora allata]] produce the [[juvenile hormone]], whose effect is to prevent the development of adult characteristics while allowing [[ecdysis]]. Therefore, the insect is subject to a series of molting, controlled by [[Ecdysone]], until the production of juvenile hormone ceases and metamorphosis occurs. ==Amphibian metamorphosis== [[Image:Tadpole (PSF).png|thumb|150px|right|Stages in the metamorphosis of a frog.]] [[Amphibian]] metamorphosis undergoes a single change from larvae, called a [[tadpole]], to an adult. In the typical amphibian lifecycle, eggs are laid in water. The tadpole then emerges from the egg, and swims freely within the water. The tadpole has gills, a tail and a small circular mouth. The tadpole will grow, until it begins metamorphosis. Metamorphosis begins with the development of the hind legs, then the front legs. The lungs develop, and the tadpole begins to swim to the surface of the water to breathe. The intestine shortens to accommodate a carnivorous diet, and the eyes migrate rostrally and dorsally. In [[frog]]s the tail is absorbed by the body, for the last stage of metamorphosis. There are many deviations from the typical amphibian lifecycle. Some species of [[salamander]] do not need to metamorphose to be sexually mature, and will only metamorphose under certain environmental stresses. Many species of frog from the [[tropics]] lay their eggs on land, where the tadpoles undergo metamorphosis within the egg. Once they hatch, they are immature copies of the adults, sometimes possessing a tail which is re-absorbed in a couple of days. ==See also== * [[Ametabolism]] * [[Hypermetamorphosis]] * [[Morphogenesis]] {{Developmental biology}} ==References== {{reflist}} * Davies, R.G., "Outlines of Entomology", Chapman and Hall: chapter 3 * Williamson D I (2003). "The Origins of Larvae", xviii + 261 pp, ISBN 1-4020-1514-3. Kluwer. Dordrecht. ==External links== * [http://www.amonline.net.au/insects/insects/metamorphosis.htm Description of metamorphosis and its different forms] * [http://www.earthlife.net/insects/lepidop1.html Info on butterflies and butterfly metamorphosis] * [http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/I/InsectHormones.html Info on insect hormones] [[Category:Developmental biology]] [[Category:Animal anatomy]] [[Category:Greek loanwords]] [[bg:Метаморфоза]] [[cs:Proměna (biologie)]] [[de:Metamorphose (Zoologie)]] [[es:Metamorfosis (biología)]] [[fa:مسخ]] [[fr:Métamorphose (biologie)]] [[gl:Metamorfose]] [[hr:Preobrazba (zoologija)]] [[id:Metamorfosis]] [[it:Metamorfosi (zoologia)]] [[lt:Metamorfozė]] [[nl:Metamorfose (biologie)]] [[ja:変態]] [[no:Metamorfose (biologi)]] [[nov:Metamorfose]] [[pl:Metamorphose]] [[pt:Metamorfose]] [[ro:Metamorfoză]] [[ru:Метаморфоз]] [[simple:Metamorphosis]] [[sr:Метаморфоза (биологија)]] [[su:Métamorfosis]] [[vi:Biến thái hoàn toàn]] [[tr:Metamorfoz (biyoloji)]] [[zh:变态 (生物)]]