In Biology, a scale is a small rigid plate which emerges from the Derme of a Animal to reinforce its protection. One speaks about scale S in animals as various as the tortoise, the lizard, the snake, fish, the pangolin or the butterfly, but also to indicate similar structures at the plants.

Scales cosmoïdes

Their internal layer is made lamellate bone. Above, is a spongy or vascular bone or a layer of Cosmine, a material close to the Dentine. The external part of the scale is covered with Kératine.
Ces scales meets only at some crossoptérygiens fossil.
Le Cœlacanthe has scales of a very close type, more fines and deprived of cosmine.

Placoid scales

These scales meet at the Chondrichtyens and are of structure comparable with that of the Dent S, consisted of Dentine covered with enamel.

Like the scales cosmodïdes, they derive from scales originally present at fossil species of the primary education, the Ostracoderme S and the placodermes. Their basal layer is made up of lamellate bone and, at the ostéychtyens, evolved/moved to give the placoid scales. The roadbase, made up of dentine and enamel, evolved/moved to give the dentils of the chondrichtyens.

Scales ganoïdes

The scales ganoïdes meet at the Lepisosteidae (family of the Semionotiformes) and the Polypteridae. The scales ganoïdes are similar to the scales cosmoïdes, but a layer of Ganoïne recovers the cosmine under enamel. These scales are brilliant and hard.

Scales leptoïdes or élasmoïdes

The scales élamoïdes meet at the Ostéichtyens. They present in two forms, cténoïde and cycloid.
- the cycloid scales have a soft edge and more frequently meet at the very old species like the Saumon or the carp.
- the scales cténoïdes are roughcast small spines laid out in rows on the edge of the scale. These scales more frequently meet at derived species, as in the kind Pomoxis or the red mullet ( Mullus barbutus )
- the placoid scales of the ostéichtyens grow by addition of concentric layers. They covered with a transparent and smooth tegument increasing their Hydrodynamic character . They are laid out in order to overlap partially, in the direction going of the head to the tail of the animal. This provision, similar to that used for the tiles of the roofs, makes it possible to reduce the trail of the animal at the time of the stroke.

Scales of butterflies

The lépidoptères have membranous wings covered with powdery scales. These scales are flattened silks. The thickness of silks being close the wavelength of the visible light, the wings of many diurnal species appear iridescent because of the phenomenon of Interférence S luminous.
La provision of the scales, and their molecular structure of surface very regular and are treated on a hierarchical basis on the scales microphone but also nanometric.

They have functions still badly included/understood which can be implied in the control of the flight, and perhaps of the complex functions related to the reflection of the light which could be implied in the orientation of the butterflies, the communication between butterflies, or their camouflage for certain species.
On studies them for possibly creating products bio-inspired. A study showed that the optical answer of the wings of butterflies " Morpho sulkowskyi " in the presence of various kinds of vapors (water, methanol, trans-1,2-DCE) was optically largely more precise and sensitive that of the optical sensors available in the field of the Nanotechnologie S. the spectra reflected by the scales provides information on nature and the content of vapors, making it possible for example to differentiate and identify the presence of water, of Méthanol, ethanol or Isomère S of Dichloroéthylène, with an answer on all the spectral range to various wavelengths. One is unaware of still if the eye and the brain of the butterfly, or the antenna S of the moth retroact according to the wavelength reflected by the scales, but it is known that these animals are sensitive to the light and besides for this reason often victims of the phenomenon known as of luminous Pollution.

Scale reptile

The scales of the Reptile S are presented in three forms:
  • cycloid
  • granular or ducted.

Their composition and close to that of the Nail S.

Tortoise

All the turtles, excluded the tortoises lute, have scales. They are fixed on the skin and the carapaces. Easy to work, the man in particular use the scales of the carapaces since millenia like object of ornament. They are quoted like goods in the Tour of the sea Érythrée towards. The scales of overlapping Tortue are more the appraisals of the scales of tortoise because they are thickest and more chatoyantes. Only one overlapping tortoise produces between 0,75 and 1,5 kg of scale with an average output of approximately a kilogram. This scale present of the hot colors and, in the skilful hands of craftsmen, it can be welded, moulded, cut out and carved. Because of the threats which weigh on the marine tortoises, this trade is interdict in many countries of the world.

Japanese who remains the first amateurs, calls the scales of tortoise bekko , the Chinese name them tai mei . The current price of certain objects in scale do one of the products of the most invaluable animals of it. The industry of the bekko remains active but, in theory, continuous on existing stocks.

Other types of scales

The Oiseau X also have scales called Scutelle S, generally on their legs. The Plume S are also considered like derived from the scales.

Some Mammifère S has scales, such as the Pangolin. They are derived from Poil S.

Certain parts of plants bear also the name of scale (root S, fruits, trunks, bark, bud S…)

See too

External bonds

Random links:Gustav Fechner | 1937 in sport | Pascal Vrebos | Nick 13 | Fights of Malta of August 24th, 1800 | Etymology of Scale