Seta

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In biology, setae /ˈst/ (singular seta /ˈstə/ ; from the Latin word for "bristle") are any of a number of different bristle- or hair-like structures on living organisms.

Contents

Animal setae

Invertebrates

Setae on the foreleg of a mayfly Isonychia Foreleg.jpg
Setae on the foreleg of a mayfly

Annelid setae are stiff bristles present on the body. They help, for example, earthworms 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 (a group including earthworms) are largely composed of chitin. [1] They are classified according to the limb to which they are attached; for instance, notosetae are attached to notopodia; neurosetae to neuropodia. [2]

Crustaceans have mechano- and chemosensory setae. [3] Setae are especially present on the mouthparts of crustaceans [3] and can also be found on grooming limbs. [4] In some cases, setae are modified into scale like structures. [4] 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. Depending partly on their form and function, setae may be called hairs, macrotrichia, chaetae , or scales . The setal membrane is not cuticularized and movement is possible. 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. [5]

Deuterostomes

In 2017, a description of a new species of basal Deuterostome was published. This animal appears to have seta in the pores along the side of its body. [6] [7] [8]

Vertebrates

Close-up of the underside of a gecko's foot as it walks on vertical glass Gecko foot on glass.JPG
Close-up of the underside of a gecko's foot as it walks on vertical glass
Common House Geckos, mating on a vertical glass window and showing lamellae under the feet Hemidactylus frenatus mating, ventral view.jpg
Common House Geckos, mating on a vertical glass window and showing 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. [9]

Fungal setae

In mycology, "setae" refer to dark brown, thick-walled, thorn-like cystidia found in corticioid and poroid fungi in the family Hymenochaetaceae. [11] 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, 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. [12]

Chaetoceros setae

In the diatom family Chaetocerotaceae, "seta" refers to the hairlike outgrowths of the valve, i.e. of the face of the cells. [13] 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. [9] [14] [15]

See also

Related Research Articles

Gecko Lizard belonging to the infraorder Gekkota

Geckos are small lizards belonging to the infraorder Gekkota, found in warm climates throughout the world. They range from 1.6 to 60 cm.

Van der Waals force residual attractive or repulsive forces between molecules or atomic groups that do not arise from covalent bonds nor ionic bonds

In molecular physics, the van der Waals force, named after Dutch scientist Johannes Diderik van der Waals, is a distance-dependent interaction between atoms or molecules. Unlike ionic or covalent bonds, these attractions do not result from a chemical electronic bond; they are comparatively weak and therefore more susceptible to disturbance. The van der Waals force quickly vanishes at longer distances between interacting molecules.

Crested gecko

The crested gecko or eyelash gecko is a species of gecko native to southern New Caledonia. In 1866, the crested gecko was described by a French zoologist named Alphone Guichenot. This species was thought extinct until it was rediscovered in 1994 during an expedition led by Robert Seipp. Along with several Rhacodactylus species, it is being considered for protected status by the Convention on the International Trade in Endangered Species of Wild Flora and Fauna. It is popular in the pet trade.

Adhesion

Adhesion is the tendency of dissimilar particles or surfaces to cling to one another.

Lamella (surface anatomy)

In surface anatomy, a lamella is a thin plate-like structure, often one amongst many lamellae very close to one another, with open space between. Aside from respiratory organs, they appear in other biological roles including filter feeding and the traction surfaces of geckos.

Fibril

Fibrils are structural biological materials found in nearly all living organisms. Not to be confused with fibers or filaments, fibrils tend to have diameters ranging from 10-100 nanometers. Fibrils are not usually found alone but rather are parts of greater hierarchical structures commonly found in biological systems. Due to the prevalence of fibrils in biological systems, their study is of great importance in the fields of microbiology, biomechanics, and materials science.

Synthetic setae

Synthetic setae emulate the setae found on the toes of a gecko and scientific research in this area is driven towards the development of dry adhesives. Geckos have no difficulty mastering vertical walls and are apparently capable of adhering themselves to just about any surface. The five-toed feet of a gecko are covered with elastic hairs called setae and the ends of these hairs are split into nanoscale structures called spatulae. The sheer abundance and proximity to the surface of these spatulae make it sufficient for van der Waals forces alone to provide the required adhesive strength. Following the discovery of the gecko's adhesion mechanism in 2002, which is based on van der Waals forces, biomimetic adhesives have become the topic of a major research effort. These developments are poised to yield families of novel adhesive materials with superior properties which are likely to find uses in industries ranging from defense and nanotechnology to healthcare and sport.

Scopulae, or scopula pads, are dense tufts of hair at the end of a spiders's legs. They are found mostly on hunting spiders, especially Lycosidae and Salticidae. Scopulae consist of microscopic hairs, known as setae, which are each covered in even smaller hairs called setules or "end feet", resulting in a large contact area.

Glossary of entomology terms List of definitions of terms and concepts commonly used in the study of entomology

This glossary of entomology describes terms used in the formal study of insect species by entomologists.

Arthropod mouthparts

The mouthparts of arthropods have evolved into a number of forms, each adapted to a different style or mode of feeding. Most mouthparts represent modified, paired appendages, which in ancestral forms would have appeared more like legs than mouthparts. In general, arthropods have mouthparts for cutting, chewing, piercing, sucking, shredding, siphoning, and filtering. This article outlines the basic elements of four arthropod groups: insects, myriapods, crustaceans and chelicerates. Insects are used as the model, with the novel mouthparts of the other groups introduced in turn. Insects are not, however, the ancestral form of the other arthropods discussed here.

Molecular self-assembly Molecules adopt a defined arrangement without guidance or management from an outside source

Molecular self-assembly is the process by which molecules adopt a defined arrangement without guidance or management from an outside source. There are two types of self-assembly. These are intramolecular self-assembly and intermolecular self-assembly. Commonly, the term molecular self-assembly refers to intermolecular self-assembly, while the intramolecular analog is more commonly called folding.

Dry glue is an adhesion product based upon the adaptations of geckos' feet that allow them to climb sheer surfaces such as vertical glass. Synthetic equivalents use carbon nanotubes as synthetic setae on reusable adhesive patches.

This glossary describes the terms used in formal descriptions of spiders; where applicable these terms are used in describing other arachnids.

Arthropod cuticle

The cuticle forms the major part of the integument of the Arthropoda. It includes most of the material of the exoskeleton of the insects, Crustacea, Arachnida, and Myriapoda.

Gecko feet

The feet of geckos have a number of specializations. Their surfaces can adhere to any type of material with the exception of Teflon (PTFE). This phenomenon can be explained with three elements:

The Diptera is a very large and diverse order of mostly small to medium-sized insects. They have prominent compound eyes on a mobile head, and one pair of functional, membraneous wings, which are attached to a complex mesothorax. The second pair of wings, on the metathorax, are reduced to halteres. The order's fundamental peculiarity is its remarkable specialization in terms of wing shape and the morpho-anatomical adaptation of the thorax – features which lend particular agility to its flying forms. The filiform, stylate or aristate antennae correlate with the Nematocera, Brachycera and Cyclorrhapha taxa respectively. It displays substantial morphological uniformity in lower taxa, especially at the level of genus or species. The configuration of integumental bristles is of fundamental importance in their taxonomy, as is wing venation. It displays a complete metamorphosis, or holometabolous development. The larvae are legless, and have head capsules with mandibulate mouthparts in the Nematocera. The larvae of "higher flies" (Brachycera) are however headless and wormlike, and display only three instars. Pupae are obtect in the Nematocera, or coarcate in Brachycera.

Arthropod adhesion

Arthropods, including insects and spiders, make use of smooth adhesive pads as well as hairy pads for climbing and locomotion along non-horizontal surfaces. Both types of pads in insects make use of liquid secretions and are considered 'wet'. Dry adhesive mechanisms primarily rely on van der Waals’ forces and are also used by organisms other than insects. The fluid provides capillary and viscous adhesion and appears to be present in all insect adhesive pads. Little is known about the chemical properties of the adhesive fluids and the ultrastructure of the fluid producing cells is currently not extensively studied. Additionally, both hairy and smooth types of adhesion have evolved separately numerous times in insects. Few comparative studies between the two types of adhesion mechanisms have been done and there is a lack of information regarding the forces that can be supported by these systems in insects. Additionally, tree frogs and some mammals such as the arboreal possum and bats also make use of smooth adhesive pads. The use of adhesive pads for locomotion across non-horizontal surfaces is a trait that evolved separately in different species, making it an example of convergent evolution. The power of adhesion allows these organisms to be able to climb on almost any substance.

Self-cleaning surfaces are a class of materials with the inherent ability to remove any debris or bacteria from their surfaces in a variety of ways. The self-cleaning functionality of these surfaces are commonly inspired by natural phenomena observed in lotus leaves, gecko feet, and water striders to name a few. The majority of self-cleaning surfaces can be placed into three categories: 1) Superhydrophobic, 2) Superhydrophilic, and 3) Photocatalytic.

Sticky pads are friction devices used to prevent objects from sliding on a surface, by effectively increasing the friction between the object and the surface.

Microsuction tape is a material for sticking objects to surfaces such as furniture, dashboards, walls, etc. One side is usually attached to the base surface by a classical adhesive. Objects are attached to the other side by pressing them against the tape. They stick to the tape due to small bubbles (cavities) on the surface of the tape. These contain air, which is squeezed out when the surface of an object is pressed against the surface of the tape. Due to sealing properties of the material, when the object is pulled off the surface, a vacuum is created in the cavities. Due to external air pressure, this creates a force that prevents the object from being removed from the surface, a mechanism similar to that of a suction cup.

References

  1. Hyman, H.L. (1966). "Further Notes on the Occurrence of Chitin in Invertebrates" (PDF). Biological Bulletin. 130 (1): 1–149. doi:10.2307/1539955. JSTOR   1539955.
  2. 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. doi:10.1017/s0094837300010009. JSTOR   2400789.
  3. 1 2 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" (PDF). Zoological Journal of the Linnean Society. 142 (2): 233–252. doi:10.1111/j.1096-3642.2004.00132.x.
  4. 1 2 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. doi:10.1016/j.jcz.2011.04.004.
  5. Hellier, FF; Warin, RP (1967). "Caterpillar Dermatitis". Br Med J. 2 (5548): 346–8. doi:10.1136/bmj.2.5548.346. PMC   1841743 . PMID   6023131.
  6. 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:2017Natur.542..228H. doi:10.1038/nature21072. ISSN   0028-0836. PMID   28135722. S2CID   353780.
  7. Wade, Nicholas (30 January 2017). "This Prehistoric Human Ancestor Was All Mouth". New York Times . Retrieved 31 January 2017.
  8. Khan, Amina (31 January 2017). "Humans, meet the ancient sea creature at the other end of your family tree". Los Angeles Times. Retrieved 1 February 2017.
  9. 1 2 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:10.1163/156856107782328399. ISSN   0169-4243. S2CID   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.
  10. Properties, Principles, and Parameters of the Gecko Adhesive System
  11. Kirk PM, Cannon PF, Minter DW, Stalpers JA (2008). Dictionary of the Fungi (10th ed.). Wallingford: CABI. p.  116. ISBN   978-0-85199-826-8.
  12. Raven, Peter H.; Evert, R.F. & Eichhorn, S.E. (2005): Biology of Plants (7th ed.). W.H. Freeman and Company.
  13. 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.
  14. "Engineers create new adhesive that mimics gecko toe hairs". physorg.com. Retrieved 19 November 2018.
  15. Setae Research Archived 2011-06-06 at the Wayback Machine