Direct development

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.¹ 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.²

Examples

Amphibians have developed direct development multiple times (convergent evolution),³ which includes groups such as:
- Brachycephaloidea⁴
- Brevicipitidae⁵⁶
- Arthroleptis⁵
Some arthropods also undergo direct development, such as ametabolous taxa like springtails.⁷ Various crustacean groups independently developed direct development, such as:
- Aeglidae⁸
- Crayfish⁸
- Freshwater and terrestrial crabs⁸⁹¹⁰¹¹

References

Fang Yan; Xiaolong Liu; Yinpeng Zhang; Zhiyong Yuan (May 28, 2021). "Direct development of the bush frog Raorchestes longchuanensis (Yang and Li 1978) under laborary conditions in Southern China". Journal of Natural History. 55 (1–2): 123–132. doi:10.1080/00222933.2021.1895349. S2CID 236202923. Retrieved March 7, 2023.
Jens Rolff; Paul R. Johnston; Stuart Reynolds (August 26, 2019). "Complete metamorphosis of insects". Philos Trans R Soc Lond B Biol Sci. 374 (1783). doi:10.1098/rstb.2019.0063. PMC 6711294. PMID 31438816.
H. Christoph Liedtke; John J. Wiens; Ivan Gomez-Mestre (17 November 2022). "The evolution of reproductive modes and life cycles in amphibians". Nature Communications. 13. doi:10.1038/s41467-022-34474-4. PMC 9672123.
Hedges, S. Blair; Duellman, William E.; Heinicke, Matthew P. (2008-03-31). "New World direct-developing frogs (Anura: Terrarana): Molecular phylogeny, classification, biogeography, and conservation". Zootaxa. 1737 (1): 1–182–1–182. doi:10.11646/zootaxa.1737.1.1. ISSN 1175-5334.
"The evolution of reproductive diversity in Afrobatrachia: A phylogenetic comparative analysis of an extensive radiation of African frogs". Evolution. 70 (9): 2017–2032. 8 August 2016. doi:10.1111/evo.12997. PMC 5129497. PMID 27402182.
"Reproduction in Brevicipitid Frogs (Amphibia: Anura: Brevicipitidae)—Evidence from Probreviceps M. Macrodactylus". Copeia. 3: 726–733. September 2007. doi:10.1643/0045-8511(2007)2007[726:RIBFAA]2.0.CO;2.
Scott F. Gilbert (2000). "Metamorphosis: The Hormonal Reactivation of Development". Developmental Biology (6 ed.). Sunderland, MA: Sinauer Associates. Retrieved March 19, 2023.
"Direct Development and Posthatching Brood Care as Key Features of the Evolution of Freshwater Decapoda and Challenges for Conservation". A Global Overview of the Conservation of Freshwater Decapod Crustaceans. October 2016. pp. 169–198. doi:10.1007/978-3-319-42527-6_6.
"Making the grade: Physiological adaptations to terrestrial environments in decapod crabs". Arthropod Structure & Development. 64. September 2021. doi:10.1016/j.asd.2021.101089.
Burggren, W.W.; McMahon, B.R., eds. (1988). Biology of the Land Crabs. Cambridge University Press. pp. 53–54. ISBN 978-0521306904.
Tan, C.G.S.; Ng, P.K.L. (1995). "Geosesarma notophorum sp. nov. (Decapoda, Brachyura, Grapsidae, Sesarminae), a Terrestrial Crab from Sumatra, with Novel Brooding Behaviour". Crustaceana. 68 (3): 390–395. doi:10.1163/156854095X00557.

[Paper-1] Fang Yan; Xiaolong Liu; Yinpeng Zhang; Zhiyong Yuan (May 28, 2021). "Direct development of the bush frog Raorchestes longchuanensis (Yang and Li 1978) under laborary conditions in Southern China". Journal of Natural History. 55 (1–2): 123–132. doi:10.1080/00222933.2021.1895349. S2CID 236202923. Retrieved March 7, 2023.

[Morph-2] Jens Rolff; Paul R. Johnston; Stuart Reynolds (August 26, 2019). "Complete metamorphosis of insects". Philos Trans R Soc Lond B Biol Sci. 374 (1783). doi:10.1098/rstb.2019.0063. PMC 6711294. PMID 31438816.

[3] H. Christoph Liedtke; John J. Wiens; Ivan Gomez-Mestre (17 November 2022). "The evolution of reproductive modes and life cycles in amphibians". Nature Communications. 13. doi:10.1038/s41467-022-34474-4. PMC 9672123.

[:0-4] Hedges, S. Blair; Duellman, William E.; Heinicke, Matthew P. (2008-03-31). "New World direct-developing frogs (Anura: Terrarana): Molecular phylogeny, classification, biogeography, and conservation". Zootaxa. 1737 (1): 1–182–1–182. doi:10.11646/zootaxa.1737.1.1. ISSN 1175-5334.

[Radiation-5] "The evolution of reproductive diversity in Afrobatrachia: A phylogenetic comparative analysis of an extensive radiation of African frogs". Evolution. 70 (9): 2017–2032. 8 August 2016. doi:10.1111/evo.12997. PMC 5129497. PMID 27402182.

[6] "Reproduction in Brevicipitid Frogs (Amphibia: Anura: Brevicipitidae)—Evidence from Probreviceps M. Macrodactylus". Copeia. 3: 726–733. September 2007. doi:10.1643/0045-8511(2007)2007[726:RIBFAA]2.0.CO;2.

[Gil-7] Scott F. Gilbert (2000). "Metamorphosis: The Hormonal Reactivation of Development". Developmental Biology (6 ed.). Sunderland, MA: Sinauer Associates. Retrieved March 19, 2023.

[Decapoda-8] "Direct Development and Posthatching Brood Care as Key Features of the Evolution of Freshwater Decapoda and Challenges for Conservation". A Global Overview of the Conservation of Freshwater Decapod Crustaceans. October 2016. pp. 169–198. doi:10.1007/978-3-319-42527-6_6.

[9] "Making the grade: Physiological adaptations to terrestrial environments in decapod crabs". Arthropod Structure & Development. 64. September 2021. doi:10.1016/j.asd.2021.101089.

[Burggren1988-10] Burggren, W.W.; McMahon, B.R., eds. (1988). Biology of the Land Crabs. Cambridge University Press. pp. 53–54. ISBN 978-0521306904.

[Tan1995-11] Tan, C.G.S.; Ng, P.K.L. (1995). "Geosesarma notophorum sp. nov. (Decapoda, Brachyura, Grapsidae, Sesarminae), a Terrestrial Crab from Sumatra, with Novel Brooding Behaviour". Crustaceana. 68 (3): 390–395. doi:10.1163/156854095X00557.

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