{{Short description|Growth to adulthood without metamorphosis}} [[File:Development of fluorescence in Brachycephalus ephippium.jpg|thumb|Direct development in the pumpkin toadlet ''Brachycephalus ephippium'']] '''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.<ref name=Paper>{{cite journal|url=https://www.tandfonline.com/doi/abs/10.1080/00222933.2021.1895349|accessdate=March 7, 2023|title=Direct development of the bush frog Raorchestes longchuanensis (Yang and Li 1978) under laborary conditions in Southern China|journal=Journal of Natural History|pages=123–132|author1=Fang Yan|author2=Xiaolong Liu|author3=Yinpeng Zhang|author4= Zhiyong Yuan|date=May 28, 2021|volume=55 |issue=1–2 |doi=10.1080/00222933.2021.1895349|s2cid=236202923 |url-access=subscription}}</ref> 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.<ref name=Morph>{{cite journal|title=Complete metamorphosis of insects|author1=Jens Rolff|author2= Paul R. Johnston|author3= Stuart Reynolds|doi=10.1098/rstb.2019.0063|date=August 26, 2019|pmid= 31438816|volume=374|issue=1783|journal=Philos Trans R Soc Lond B Biol Sci|pmc=6711294 }}</ref>
==Examples== * Amphibians have developed direct development multiple times (convergent evolution),<ref>{{cite journal |last1=H. Christoph Liedtke |last2=John J. Wiens |last3=Ivan Gomez-Mestre |title=The evolution of reproductive modes and life cycles in amphibians |journal=Nature Communications |date=17 November 2022 |volume=13 |doi=10.1038/s41467-022-34474-4|pmc=9672123 }}</ref> which includes groups such as: ** Brachycephaloidea<ref name=":0">{{Cite journal |last1=Hedges |first1=S. Blair |last2=Duellman |first2=William E. |last3=Heinicke |first3=Matthew P. |date=2008-03-31 |title=New World direct-developing frogs (Anura: Terrarana): Molecular phylogeny, classification, biogeography, and conservation |url=https://www.mapress.com/zt/article/view/zootaxa.1737.1.1 |journal=Zootaxa |language=en |volume=1737 |issue=1 |pages=1–182–1–182 |doi=10.11646/zootaxa.1737.1.1 |issn=1175-5334|url-access=subscription }}</ref> ** Brevicipitidae<ref name="Radiation"/><ref>{{cite journal |title=Reproduction in Brevicipitid Frogs (Amphibia: Anura: Brevicipitidae)—Evidence from Probreviceps M. Macrodactylus |journal=Copeia |date=September 2007 |volume=3 |pages=726-733 |doi=10.1643/0045-8511(2007)2007[726:RIBFAA]2.0.CO;2}}</ref> ** ''Arthroleptis''<ref name="Radiation">{{cite journal |title=The evolution of reproductive diversity in Afrobatrachia: A phylogenetic comparative analysis of an extensive radiation of African frogs |journal=Evolution |date=8 August 2016 |volume=70 |issue=9 |pages=2017–2032 |doi=10.1111/evo.12997 |pmid=27402182|pmc=5129497 }}</ref> * Some arthropods also undergo direct development, such as ametabolous taxa like springtails.<ref name=Gil>{{cite book|accessdate=March 19, 2023|url=https://www.ncbi.nlm.nih.gov/books/NBK9986/|title=Developmental Biology|edition=6|author=Scott F. Gilbert|location=Sunderland, MA |publisher=Sinauer Associates|year= 2000|chapter= Metamorphosis: The Hormonal Reactivation of Development}}</ref> Various crustacean groups independently developed direct development, such as: ** Aeglidae<ref name="Decapoda"/> ** Crayfish<ref name="Decapoda"/> ** Freshwater and terrestrial crabs<ref name="Decapoda">{{cite book |title=A Global Overview of the Conservation of Freshwater Decapod Crustaceans |date=October 2016 |pages=169-198 |chapter=Direct Development and Posthatching Brood Care as Key Features of the Evolution of Freshwater Decapoda and Challenges for Conservation |doi=10.1007/978-3-319-42527-6_6}}</ref><ref>{{cite journal |title=Making the grade: Physiological adaptations to terrestrial environments in decapod crabs |journal=Arthropod Structure & Development |date=September 2021 |volume=64 |doi=10.1016/j.asd.2021.101089|doi-access=free }}</ref><ref name="Burggren1988">{{cite book|editor1= Burggren, W.W.|editor2= McMahon, B.R.|title= Biology of the Land Crabs|url= https://books.google.com/books?id=RR09AAAAIAAJ&pg=PA53|year= 1988|publisher= Cambridge University Press|isbn= 978-0521306904|pages= 53–54}}</ref><ref name="Tan1995">{{cite journal|last1 =Tan|first1= C.G.S.|last2= Ng|first2= P.K.L.|title= ''Geosesarma notophorum'' sp. nov. (Decapoda, Brachyura, Grapsidae, Sesarminae), a Terrestrial Crab from Sumatra, with Novel Brooding Behaviour |journal= Crustaceana |volume= 68|issue= 3|year= 1995|pages= 390–395|doi= 10.1163/156854095X00557}}</ref>
==References== {{reflist}}
Category:Developmental biology Category:Animal anatomy
{{biology-stub}}