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
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
Vertebrates
Close-up of the underside of a gecko's foot as it walks on vertical glassCommon house geckos mating on a vertical glass window and showing lamellae under the feet
Gekko's seta: According to Kellar Autumn, "Two front feet of a tokay gecko (
Gekko gecko) can withstand 20.1 N of force parallel to the surface with 227 mm2 of pad area (Irschick et al. 1996). The foot of a tokay bears approximately 3600 tetrads of setae per mm2, or 14,400 setae per mm2 (Schleich and Kastle 1986; pers. obs.). Consequently, a single seta should produce an average force of 6.2 pN, and an average shear stress of 0.090 N⋅mm−1 (0.9 atm). However, single setae proved both much less sticky and much more sticky than predicted by whole animal measurements, under varying experimental conditions, implying that attachment and detachment in gecko setae are mechanically controlled (Autumn et al. 2000)."[7]
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.[8] However, in 2022, Saccorhytus is considered to be an early ecdysozoan, and was described as having "lacked setae".[9]
Though mainly microscopic, the setae of some species may be sufficiently prominent to be visible with a hand lens.
Plant setae
In
parasitic. Setae are not present in all mosses, but in some species they may reach 15 to 20 centimeters in height.[11]
Chaetoceros setae
In the diatom family Chaetocerotaceae, "seta" refers to the hairlike outgrowths of the valve, i.e. of the face of the cells.[12] 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.[6][13][14]
. 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.
^Properties, Principles, and Parameters of the Gecko Adhesive System
^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.
