Seta

Quality 0.50 · 3 views · Updated 2 months ago

Hair-like structure on living organisms

title: "Seta" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["plant-anatomy", "animal-hair", "fungal-morphology-and-anatomy"] description: "Hair-like structure on living organisms" topic_path: "science/biology" source: "https://en.wikipedia.org/wiki/Seta" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Hair-like structure on living organisms ::

In biology, setae (; seta ; ) are any of a number of different bristle- or hair-like structures on living organisms.

Animal setae

Protostomes

::figure[src="https://upload.wikimedia.org/wikipedia/commons/4/44/Isonychia_Foreleg.jpg" caption="Setae on the foreleg of a [[mayfly"] ::

Depending partly on their form and function, protostome setae may be called macrotrichia, chaetae, scales, or informally, hairs. The setal membrane is not cuticularized, so movement is possible.

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

Crustaceans have mechano- and chemosensory setae. Setae are especially present on the mouthparts of crustaceans and can also be found on grooming limbs. In some cases, setae are modified into scale like structures. Setae on the legs of krill and other small crustaceans help them to gather phytoplankton. It captures them and allows them to be eaten.

Setae on the 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. Some insects, such as Eriogaster lanestris larvae, use setae as a defense mechanism, as they can cause dermatitis when they come into contact with skin. Diptera setae are bristles present throughout the body and function as mechanoreceptors.

Deuterostomes

Vertebrates

::figure[src="https://upload.wikimedia.org/wikipedia/commons/b/b2/Gecko_foot_on_glass.JPG" caption="Close-up of the underside of a gecko's foot as it walks on vertical glass"] ::

::figure[src="https://upload.wikimedia.org/wikipedia/commons/f/f6/Hemidactylus_frenatus_mating,_ventral_view.jpg" caption="lamellae]] under the feet"] ::

The pads on a gecko's feet are small hair-like processes 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. A 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.

Classification uncertain

In 2017, a description of a new species of basal deuterostome called Saccorhytus was published. This animal appears to have seta in the pores along the side of its body. However, in 2022, Saccorhytus is considered to be an early ecdysozoan, and was described as having "lacked setae".

Fungal setae

::figure[src="https://upload.wikimedia.org/wikipedia/commons/6/6d/Phellinus_gilvus_setae_2.jpg" caption="Pointed setae protruding into the fertile surface tubes of the bracket fungus ''[[Fuscoporia gilva]]''"] ::

In mycology, "setae" refer to dark-brown, thick-walled, thornlike cystidia found in corticioid and poroid fungi in the family Hymenochaetaceae. Though mainly microscopic, the setae of some species may be sufficiently prominent to be visible with a hand lens.

Plant setae

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

Chaetoceros setae

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

Synthetic setae

Synthetic setae are a class of synthetic adhesives that detach at will, sometimes called resettable adhesives, yet display substantial stickiness. The development of such synthetic materials is a matter of current research.

References

(1966). "Further Notes on the Occurrence of Chitin in Invertebrates". Biological Bulletin.
(1990). "A reassessment of the enigmatic Burgess Shale fossil ''Wiwaxia corrugata'' (Matthew) and its relationship to the polychaete ''Canadia spinosa'' Walcott". Paleobiology.
(2004). "Revising the definition of the crustacean seta and setal classification systems based on examinations of the mouthpart setae of seven species of decapods". Zoological Journal of the Linnean Society.
(2011). "Morphological diversity of setae on the grooming legs in Anomala (Decapoda: Reptantia) revealed by scanning electron microscopy". Zoologischer Anzeiger.
(1967). "Caterpillar Dermatitis". Br Med J.
Santos, Daniel. (2007). "Directional adhesion for climbing: theoretical and practical considerations". Journal of Adhesion Science and Technology.
(2006). "Biological adhesives". Springer.
(2017). "Meiofaunal deuterostomes from the basal Cambrian of Shaanxi (China)". Nature.
(2022-08-17). "Saccorhytus is an early ecdysozoan and not the earliest deuterostome". Nature.
(2008). "Dictionary of the Fungi". CABI.
{{aut. [[Peter H. Raven. Raven, Peter H.]]; Evert, R.F. & Eichhorn, S.E. (2005): ''[[Biology of Plants]]'' (7th ed.). W.H. Freeman and Company.
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.
"Engineers create new adhesive that mimics gecko toe hairs".
link. (2011-06-06)

::callout[type=info title="Wikipedia Source"] This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page. ::