Direct development
Growth to adulthood without metamorphosis
Direct development is a concept in biology. It refers to forms of growth to adulthood that do not involve metamorphosis. An animal undergoes direct development if the immature organism resembles a small adult rather than having a distinct larval form. A frog that hatches out of its egg as a small frog undergoes direct development. A frog that hatches out of its egg as a tadpole does not.
Direct development is the opposite of complete metamorphosis. An animal undergoes complete metamorphosis if it becomes a non-moving thing, for example a pupa in a cocoon, between its larval and adult stages.
01Examples
Direct development is ancestral in tetrapodomorphs. It has been suggested that either metamorphosis emerged in the last common ancestor of modern amphibians and amniotes (crown Tetrapoda), but that the common ancestor of amniotes reverted back to direct development, or that metamorphosis convergently evolved both in temnospondyls and their modern amphibian descendants as well as seymouriamorphs.
- Amphibians have developed direct development multiple times (convergent evolution), which includes groups such as:
- Some arthropods also undergo direct development, such as ametabolous taxa like springtails. Various crustacean groups independently developed direct development, such as:
Sources and credits
This article is adapted from the Wikipedia article “Direct development”, written by its contributors and licensed under CC BY-SA 4.0. Fathomly has changed the layout, removed citation markers, navigation and maintenance notices, and adjusted punctuation. This adapted version is shared under the same license. For references, see the original article.
Images, from Wikimedia Commons:
- Development of fluorescence in Brachycephalus ephippium.jpg by Sandra Goutte, Matthew J. Mason, Marta M. Antoniazzi, Carlos Jared, Didier Merle, Lilian Cazes, Luís Felipe Toledo, Hanane el-Hafci, Stéphane Pallu, Hugues Portier, Stefan Schramm, Pierre Gueriau & Mathieu Thoury, CC BY-SA 4.0
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