From en.wikipedia.org:
[Hair-like structure on living organisms] [Seta (disambiguation)] [Setae]
[seta]
In biology, SETAE ([ˈ]; [singular] SETA [ˈ]; [la]) are any of a number of
different bristle- or hair-like structures on living organisms.
** Animal setae
*** Protostomes
Depending partly on their form and function, protostome setae may be called
MACROTRICHIA, CHAETA E, 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.[1] They are classified according to the limb to
which they are attached; for instance, notosetae are attached to notopodia;
neurosetae to neuropodia.[2] The setae on polychaete worms are referred to as
chaeta due to their differing morphology.
Crustaceans have mechano- and chemosensory setae.[3] Setae are especially
present on the mouthparts of crustaceans<ref name="isopods.nhm.org"/> and can
also be found on grooming limbs.[4] In some cases, setae are modified into
scale like structures.<ref name="sciencedirect.com"/> 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.[5] Diptera setae are bristles present throughout the
body and function as mechanoreceptors.
*** Deuterostomes
**** Vertebrates
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.<ref
name=Santos2007>[last=Santos ] A Tokay gecko's two front feet can sustain 20.1
N of force parallel to the surface using approximately 14,400 setae per
mm<sup>2</sup>. This equates to ~ 6.2 pN per seta, but does not sufficiently
account for the overall stickiness behavior shown by the foot pads.[6]
*** 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.[7] However, in 2022, _Saccorhytus_ is considered
to be an early ecdysozoan, and was described as having "lacked setae".[8]
** Fungal setae
In mycology, "setae" refer to dark-brown, thick-walled, thornlike cystidia
found in corticioid and poroid fungi in the family Hymenochaetaceae.[9] 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.[10]
** Chaetoceros setae
In the diatom family Chaetocerotaceae, "seta" refers to the hairlike
outgrowths of the valve, i.e. of the face of the cells.<ref
name=Tomas97>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. 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.<ref name=Santos2007/>[11][12]
** See also
- Chaeta
- Synthetic setae
- Van der Waals force
** References
[28em]
Category:Plant anatomy Category:Animal hair Category:Fungal morphology and
anatomy