Metamorphosis

Metamorphosis is a biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body  structure through cell growth and differentiation. Some insects, amphibians, mollusks, crustaceans, Cnidarians, echinoderms  and tunicates  undergo metamorphosis, which is usually (but not always) accompanied by a change of habitat or behavior.


Scientific usage of the term is exclusive, and is not applied to general aspects of cell growth, including rapid growth spurts. References to "metamorphosis" in mammals are imprecise and only colloquial, but historically idealist ideas of transformation and monadology, as in Goethe's Metamorphosis of Plants, influenced the development of ideas of evolution.

Insect  growth and metamorphosis are controlled by hormones  synthesized by endocrine glands near the front of the body.



neurosecretory cells of an insect's brain secrete a hormone, the prothoracicotropic hormone that activates prothoracic glands, which secrete a second hormone, usually Ecdysone (a steroid), that induces metamorphosis.

Moreover, the corpora allata, a retrocerebral organ produces 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.