Metamorphosis

Pronunciation
/met-uh-MOR-fuh-sis/
Category
Physiology
Singular
metamorphosis
Plural
metamorphoses

Definition

A developmental process in which an animal undergoes a conspicuous and relatively abrupt change in body structure between distinct life stages, typically mediated by molting and involving of tissue organization, , and often or diet. In , metamorphosis proceeds through a series of () in which the old is shed and a new one expands and hardens; the final molt produces the form (), after which no further molts occur. Insects exhibit three principal modes: holometabolism (complete metamorphosis with discrete , larva, pupa, and adult stages), hemimetabolism ( with gradual transformation through nymphal instars), and ametabolism (primitively direct development without marked change).

Etymology

From Greek meta- (after, beyond) + morphe (form), referring to the change of form between life stages.

Example

A () undergoes holometabolous metamorphosis: the caterpillar through five larval instars, forms a chrysalis (pupa) during which larval tissues histolyze and reorganize into structures, and emerges as a winged adult incapable of further molting.

Synonyms

  • metamorphose (verb)

Related Terms

Usage Notes

Metamorphosis is absolute in holometabolous insects— and larvae are so divergent that they often exploit entirely different —whereas hemimetabolous change is more gradual and nymphs typically resemble adults in body plan. The term is sometimes applied more broadly to vertebrate metamorphosis (e.g., amphibian tadpoles), but in entomological contexts it refers specifically to development mediated by . Post- adults are described as until the fully hardens. Contrast with direct development (ametabolism) in and related basal hexapods, where young are miniature adults.