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

It has been suggested that 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.^[3]

Amphibians have developed direct development multiple times (convergent evolution),^[4] which includes groups such as:
- Brachycephaloidea^[5]
- Brevicipitidae^[6]^[7]
- Arthroleptis^[6]
Some arthropods also undergo direct development, such as ametabolous taxa like springtails.^[8] Various crustacean groups independently developed direct development, such as:
- Aeglidae^[9]
- Crayfish^[9]
- Freshwater and terrestrial crabs^[9]^[10]^[11]^[12]

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.
^ Pardo, Jason D.; Mann, Arjan (2026-06-18). "Direct development of stem tetrapods across the fin-to-limb transition". Science. 392 (6804): 1292–1296. doi:10.1126/science.aeb7635. ISSN 0036-8075.
^ 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.
^ ^a ^b "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.
^ ^a ^b ^c "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.

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[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] Pardo, Jason D.; Mann, Arjan (2026-06-18). "Direct development of stem tetrapods across the fin-to-limb transition". Science. 392 (6804): 1292–1296. doi:10.1126/science.aeb7635. ISSN 0036-8075.

[4] 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.

[:0-5] 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-6] "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.

[7] "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-8] Scott F. Gilbert (2000). "Metamorphosis: The Hormonal Reactivation of Development". Developmental Biology (6 ed.). Sunderland, MA: Sinauer Associates. Retrieved March 19, 2023.

[Decapoda-9] "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.

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

[Burggren1988-11] Burggren, W.W.; McMahon, B.R., eds. (1988). Biology of the Land Crabs. Cambridge University Press. pp. 53–54. ISBN 978-0521306904.

[Tan1995-12] 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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