# Seta

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Hair-like structure on living organisms

For other uses, see [Seta (disambiguation)](/source/Seta_(disambiguation)).

"Setae" redirects here. For the town of ancient Lydia, see [Setae (Lydia)](/source/Setae_(Lydia)).

Look up ***[seta](https://en.wiktionary.org/wiki/seta)*** in Wiktionary, the free dictionary.

In [biology](/source/Biology), **setae** ([/ˈsiːtiː/](https://en.wikipedia.org/wiki/Help:IPA/English); sing. **seta** [/ˈsiːtə/](https://en.wikipedia.org/wiki/Help:IPA/English); from [Latin](/source/Latin_language) **[saeta](https://en.wiktionary.org/wiki/saeta#Latin)** '[bristle](/source/Bristle)') are any of a number of different bristle- or [hair](/source/Hair)-like structures on living [organisms](/source/Organism).

## Animal setae

### Protostomes

Setae on the foreleg of a [mayfly](/source/Mayfly)

Depending partly on their form and function, protostome setae may be called **macrotrichia**, **[chaetae](/source/Chaeta)**, **[scales](/source/Scale_(insect_anatomy))**, or [informally](/source/Common_name), hairs. The setal membrane is not [cuticularized](/source/Cuticle), so movement is possible.[1]

#### Annelid

[Annelid](/source/Annelid) setae are stiff bristles present on the body. They allow [earthworms](/source/Earthworm) and their relatives to attach to the surface and prevent backsliding during [peristaltic](/source/Peristaltic) motion. These hairs make it difficult to pull a worm straight from the ground. Setae in [oligochaetes](/source/Oligochaetes) (the group including earthworms) are largely composed of [chitin](/source/Chitin).[2] They are classified according to the limb to which they are attached; for instance, notosetae are attached to [notopodia](/source/Notopodia); neurosetae to [neuropodia](/source/Neuropodia).[3] The setae on [polychaete worms](/source/Polychaete_worm) are referred to as chaeta due to their differing morphology.[4]

#### Crustacean

[Crustaceans](/source/Crustacean) have mechano- and [chemosensory](/source/Chemosensory) setae.[5] Setae are especially present on the mouthparts of crustaceans[5] and can also be found on grooming limbs.[6] In some cases, setae are modified into scale like structures.[6] Setae on the legs of [krill](/source/Krill) and other small crustaceans help them to gather [phytoplankton](/source/Phytoplankton). It captures them and allows them to be eaten.[7]

#### Insect

Setae on the [integument](/source/Integument) of insects are unicellular, meaning that each is formed from a single epidermal cell of a type called a trichogen, literally meaning "bristle generator". They are at first hollow and in most forms remain hollow after they have hardened. They grow through and project through a secondary or accessory cell of a type called a tormogen, which generates the special flexible membrane that connects the base of the seta to the surrounding [integument](/source/Integument). Some insects, such as *[Eriogaster lanestris](/source/Eriogaster_lanestris)* larvae, use setae as a defense mechanism, as they can cause dermatitis when they come into contact with skin.[8] [Diptera](/source/Fly) setae are [bristles](/source/Bristle_sensilla) present throughout the body and function as [mechanoreceptors](/source/Mechanoreceptor).

### Deuterostomes

#### Vertebrates

Close-up of the underside of a gecko's foot as it walks on vertical glass

[Common house geckos](/source/Common_house_gecko) mating on a vertical glass window and showing [lamellae](/source/Lamella_(surface_anatomy)) under the feet

The pads on a [gecko](/source/Gecko)'s feet are small hair-like [processes](/source/Process_(anatomy)) that play a role in the animal's ability to cling to vertical surfaces. The micrometer-scale setae branch into nanometer-scale projections called [spatulae](/source/Spatulae_(biology)).[9] A [Tokay gecko](/source/Tokay_gecko)'s two front feet can sustain 20.1 N of force parallel to the surface using approximately 14,400 setae per mm2. This equates to ~ 6.2 pN per seta, but does not sufficiently account for the overall stickiness behavior shown by the foot pads.[10]

### Classification uncertain

In 2017, a description of a new species of basal [deuterostome](/source/Deuterostome) called *[Saccorhytus](/source/Saccorhytus)* was published. This animal appears to have seta in the pores along the side of its body.[11] However, in 2022, *Saccorhytus* is considered to be an early [ecdysozoan](/source/Ecdysozoa), and was described as having "lacked setae".[12]

## Fungal setae

Pointed setae protruding into the fertile surface tubes of the bracket fungus *[Fuscoporia gilva](/source/Fuscoporia_gilva)*

In [mycology](/source/Mycology), "setae" refer to dark-brown, thick-walled, thornlike [cystidia](/source/Cystidia) found in [corticioid](/source/Corticioid_fungi) and [poroid fungi](/source/Polypores) in the [family](/source/Family_(taxonomy)) [Hymenochaetaceae](/source/Hymenochaetaceae).[13] Though mainly microscopic, the setae of some species may be sufficiently prominent to be visible with a hand lens.

## Plant setae

In [botany](/source/Botany), "seta" refers to the stalk supporting the [capsule](/source/Sporangium) of a [moss](/source/Moss) or [liverwort](/source/Marchantiophyta) (both closely related in a clade called "Setaphyta"), and supplying it with nutrients. The seta is part of the [sporophyte](/source/Sporophyte) and has a short foot embedded in the [gametophyte](/source/Gametophyte) on which it is [parasitic](/source/Parasitic). Setae are not present in all mosses, but in some [species](/source/Species) they may reach 15 to 20 centimeters in height.[14]

## Chaetoceros setae

In the diatom family [Chaetocerotaceae](/source/Chaetocerotaceae), "seta" refers to the hairlike outgrowths of the valve, i.e. of the face of the cells.[15] These setae have a different structure than the valve. Such setae may prevent rapid sinking and also protect the cells from grazing.[16]

## Synthetic setae

[Synthetic setae](/source/Synthetic_setae) are a class of synthetic [adhesives](/source/Adhesive) that detach at will, sometimes called resettable adhesives, yet display substantial stickiness. The development of such synthetic materials is a matter of current [research](/source/Research).[9][17][18]

## See also

- [Chaeta](/source/Chaeta)

- [Synthetic setae](/source/Synthetic_setae)

- [Van der Waals force](/source/Van_der_Waals_force#Use_by_geckos_and_arthropods)

## References

1. **[^](#cite_ref-1)** Torre-Bueno, J. R. de la (José Rollin) (1989). [*The Torre-Bueno glossary of entomology*](http://archive.org/details/torrebuenoglossa0000torr). Internet Archive. New York, N.Y., USA : New York Entomological Society in cooperation with the American Museum of Natural History. [ISBN](/source/ISBN_(identifier)) [978-0-913424-13-1](https://en.wikipedia.org/wiki/Special:BookSources/978-0-913424-13-1).

1. **[^](#cite_ref-2)** Hyman, H.L. (1966). ["Further Notes on the Occurrence of Chitin in Invertebrates"](http://www.biolbull.org/cgi/reprint/130/1/94.pdf) (PDF). *Biological Bulletin*. **130** (1): 1–149. [doi](/source/Doi_(identifier)):[10.2307/1539955](https://doi.org/10.2307%2F1539955). [JSTOR](/source/JSTOR_(identifier)) [1539955](https://www.jstor.org/stable/1539955).

1. **[^](#cite_ref-3)** Butterfield, N. J. (1990). "A reassessment of the enigmatic Burgess Shale fossil *Wiwaxia corrugata* (Matthew) and its relationship to the polychaete *Canadia spinosa* Walcott". *Paleobiology*. **16** (3): 287–303. [Bibcode](/source/Bibcode_(identifier)):[1990Pbio...16..287B](https://ui.adsabs.harvard.edu/abs/1990Pbio...16..287B). [doi](/source/Doi_(identifier)):[10.1017/s0094837300010009](https://doi.org/10.1017%2Fs0094837300010009). [JSTOR](/source/JSTOR_(identifier)) [2400789](https://www.jstor.org/stable/2400789). [S2CID](/source/S2CID_(identifier)) [88100863](https://api.semanticscholar.org/CorpusID:88100863).

1. **[^](#cite_ref-4)** Fauchald, Kristian (1977). [*The polychaete worms. Definitions and keys to the orders, families and genera*](http://hdl.handle.net/10088/3435). Los Angeles, California: Natural History Museum of Los Angeles County.

1. ^ [***a***](#cite_ref-isopods.nhm.org_5-0) [***b***](#cite_ref-isopods.nhm.org_5-1) Garm, A (2004). ["Revising the definition of the crustacean seta and setal classification systems based on examinations of the mouthpart setae of seven species of decapods"](http://isopods.nhm.org/pdfs/12763/12763.pdf) (PDF). *Zoological Journal of the Linnean Society*. **142** (2): 233–252. [doi](/source/Doi_(identifier)):[10.1111/j.1096-3642.2004.00132.x](https://doi.org/10.1111%2Fj.1096-3642.2004.00132.x).

1. ^ [***a***](#cite_ref-sciencedirect.com_6-0) [***b***](#cite_ref-sciencedirect.com_6-1) Keiler, J.; Richter, S. (2011). "Morphological diversity of setae on the grooming legs in Anomala (Decapoda: Reptantia) revealed by scanning electron microscopy". *Zoologischer Anzeiger*. **250** (4): 343–366. [Bibcode](/source/Bibcode_(identifier)):[2011ZooAn.250..343K](https://ui.adsabs.harvard.edu/abs/2011ZooAn.250..343K). [doi](/source/Doi_(identifier)):[10.1016/j.jcz.2011.04.004](https://doi.org/10.1016%2Fj.jcz.2011.04.004).

1. **[^](#cite_ref-7)** Hamner, W. M. (1988-04-01). ["Biomechanics of Filter Feeding in the Antarctic Krill Euphausia Superba: Review of Past Work and New Observations"](https://academic.oup.com/jcb/article-lookup/doi/10.2307/1548308). *Journal of Crustacean Biology*. **8** (2): 149–163. [doi](/source/Doi_(identifier)):[10.2307/1548308](https://doi.org/10.2307%2F1548308). [ISSN](/source/ISSN_(identifier)) [0278-0372](https://search.worldcat.org/issn/0278-0372).

1. **[^](#cite_ref-8)** Hellier, FF; Warin, RP (1967). ["Caterpillar Dermatitis"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1841743). *Br Med J*. **2** (5548): 346–8. [doi](/source/Doi_(identifier)):[10.1136/bmj.2.5548.346](https://doi.org/10.1136%2Fbmj.2.5548.346). [PMC](/source/PMC_(identifier)) [1841743](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1841743). [PMID](/source/PMID_(identifier)) [6023131](https://pubmed.ncbi.nlm.nih.gov/6023131).

1. ^ [***a***](#cite_ref-Santos2007_9-0) [***b***](#cite_ref-Santos2007_9-1) Santos, Daniel; Matthew Spenko; Aaron Parness; Kim Sangbae; Mark Cutkosky (2007). "Directional adhesion for climbing: theoretical and practical considerations". *Journal of Adhesion Science and Technology*. **21** (12–13): 1317–1341. [doi](/source/Doi_(identifier)):[10.1163/156856107782328399](https://doi.org/10.1163%2F156856107782328399). [ISSN](/source/ISSN_(identifier)) [0169-4243](https://search.worldcat.org/issn/0169-4243). [S2CID](/source/S2CID_(identifier)) [53470787](https://api.semanticscholar.org/CorpusID:53470787). *Gecko "feet and toes are a hierarchical system of complex structures consisting of lamellae, setae, and spatulae. The distinguishing characteristics of the gecko adhesion system have been described [as] (1) anisotropic attachment, (2) high pulloff force to preload ratio, (3) low detachment force, (4) material independence, (5) self-cleaning, (6) anti-self sticking and (7) non-sticky default state. ... The gecko's adhesive structures are made from ß-keratin (modulus of elasticity [approx.] 2 GPa). Such a stiff material is not inherently sticky; however, because of the gecko adhesive's hierarchical nature and extremely small distal features (spatulae are [approx.] 200 nm in size), the gecko's foot is able to intimately conform to the surface and generate significant attraction using van der Waals forces.*

1. **[^](#cite_ref-10)** Autumn, K.; Puthoff, J. (2006). "Properties, principles, and parameters of the gecko adhesive system". In Smith, A.M., Callow, J.A. (ed.). *Biological adhesives*. Springer. pp. 245–280. [ISBN](/source/ISBN_(identifier)) [978-3-540-31048-8](https://en.wikipedia.org/wiki/Special:BookSources/978-3-540-31048-8).{{[cite book](https://en.wikipedia.org/wiki/Template:Cite_book)}}: CS1 maint: multiple names: editors list ([link](https://en.wikipedia.org/wiki/Category:CS1_maint:_multiple_names:_editors_list))

1. **[^](#cite_ref-HanMorris2017_11-0)** Han, Jian; Morris, Simon Conway; Ou, Qiang; Shu, Degan; Huang, Hai (2017). "Meiofaunal deuterostomes from the basal Cambrian of Shaanxi (China)". *Nature*. **542** (7640): 228–231. [Bibcode](/source/Bibcode_(identifier)):[2017Natur.542..228H](https://ui.adsabs.harvard.edu/abs/2017Natur.542..228H). [doi](/source/Doi_(identifier)):[10.1038/nature21072](https://doi.org/10.1038%2Fnature21072). [ISSN](/source/ISSN_(identifier)) [0028-0836](https://search.worldcat.org/issn/0028-0836). [PMID](/source/PMID_(identifier)) [28135722](https://pubmed.ncbi.nlm.nih.gov/28135722). [S2CID](/source/S2CID_(identifier)) [353780](https://api.semanticscholar.org/CorpusID:353780).

1. **[^](#cite_ref-12)** Liu, Yunhuan; Carlisle, Emily; Zhang, Huaqiao; Yang, Ben; Steiner, Michael; Shao, Tiequan; Duan, Baichuan; Marone, Federica; Xiao, Shuhai; Donoghue, Philip C. J. (2022-08-17). ["Saccorhytus is an early ecdysozoan and not the earliest deuterostome"](https://www.nature.com/articles/s41586-022-05107-z). *Nature*. **609** (7927): 541–546. [Bibcode](/source/Bibcode_(identifier)):[2022Natur.609..541L](https://ui.adsabs.harvard.edu/abs/2022Natur.609..541L). [doi](/source/Doi_(identifier)):[10.1038/s41586-022-05107-z](https://doi.org/10.1038%2Fs41586-022-05107-z). [hdl](/source/Hdl_(identifier)):[1983/454e7bec-4cd4-4121-933e-abeab69e96c1](https://hdl.handle.net/1983%2F454e7bec-4cd4-4121-933e-abeab69e96c1). [ISSN](/source/ISSN_(identifier)) [1476-4687](https://search.worldcat.org/issn/1476-4687). [PMID](/source/PMID_(identifier)) [35978194](https://pubmed.ncbi.nlm.nih.gov/35978194). [S2CID](/source/S2CID_(identifier)) [251646316](https://api.semanticscholar.org/CorpusID:251646316).

1. **[^](#cite_ref-13)** Kirk PM, Cannon PF, Minter DW, Stalpers JA (2008). [*Dictionary of the Fungi*](https://archive.org/details/dictionaryfungit00kirk) (10th ed.). Wallingford: CABI. p. [116](https://archive.org/details/dictionaryfungit00kirk/page/n126). [ISBN](/source/ISBN_(identifier)) [978-0-85199-826-8](https://en.wikipedia.org/wiki/Special:BookSources/978-0-85199-826-8).

1. **[^](#cite_ref-14)** [Raven, Peter H.](/source/Peter_H._Raven); Evert, R.F. & Eichhorn, S.E. (2005): *[Biology of Plants](https://en.wikipedia.org/w/index.php?title=Biology_of_Plants&action=edit&redlink=1)* (7th ed.). W.H. Freeman and Company.

1. **[^](#cite_ref-Tomas97_15-0)** Tomas, C. R., Hasle G. R., Syvertsen, E. E., Steidinger, K. A., Tangen, K., Throndsen, J., Heimdal, B. R., (1997). *Identifying Marine Phytoplankton*, Academic Press.

1. **[^](#cite_ref-16)** Owari, Yuka; Nakamura, Fumi; Oaki, Yuya; Tsuda, Hiroyuki; Shimode, Shinji; Imai, Hiroaki (2022-05-09). ["Ultrastructure of setae of a planktonic diatom, Chaetoceros coarctatus"](https://www.nature.com/articles/s41598-022-11484-2). *Scientific Reports*. **12** (1): 7568. [doi](/source/Doi_(identifier)):[10.1038/s41598-022-11484-2](https://doi.org/10.1038%2Fs41598-022-11484-2). [ISSN](/source/ISSN_(identifier)) [2045-2322](https://search.worldcat.org/issn/2045-2322). [PMC](/source/PMC_(identifier)) [9085750](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9085750).

1. **[^](#cite_ref-17)** ["Engineers create new adhesive that mimics gecko toe hairs"](http://www.physorg.com/news120845139.html). *physorg.com*. Retrieved 19 November 2018.

1. **[^](#cite_ref-18)** [Setae Research](http://www.physorg.com/search/search.php?search=+Gecko%2Bsetae) [Archived](https://web.archive.org/web/20110606060332/http://www.physorg.com/search/search.php?search=+Gecko+setae) 2011-06-06 at the [Wayback Machine](/source/Wayback_Machine)

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