Scale (zoology)

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Scale (zoology)

In most biological

Biology

Biology is a branch of the natural sciences concerned with the study of living organisms and their interaction with each other and their environment ....
nomenclature, a scale (Greek

Greek language

Greek is an Indo-European languages native to the southern Balkan peninsula, the language of the Greek people. It forms an independent branch within Indo-European....
lepid, Latin squama) is a small rigid plate that grows out of an animal

Animal

Animals are a major group of multicellular, eukaryotic organisms of the Kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life....
's skin

Skin

The skin is the outer covering of the body, also known as the epidermis. It is the largest organ of the integumentary system made up of multiple layers of epithelial biological tissue, and guards the underlying muscles, bones, ligaments and organ s....
to provide protection. In lepidoptera

Lepidoptera

Lepidoptera is an order of insect that includes moths and butterfly. It is one of the most speciose orders in the class Insecta, encompassing moths and the three superfamilies of butterfly, skipper , and Hedylidae....
n (butterfly

Butterfly

A butterfly is an insect of the Order Lepidoptera. Like all Lepidoptera, butterflies are notable for their unusual Biological life cycle with a larval caterpillar stage, an inactive pupal stage, and a spectacular metamorphosis into a familiar and colourful winged adult form....
and moth

Moth

A moth is an insect closely related to the butterfly, both being of the Order Lepidoptera. The differences between butterflies and moths are more than just taxonomy....
) species, scales are plates on the surface of the insect

Insect

Insects are the biggest class of arthropods and the only ones with wings. They are the most diverse group of animals on the planet. They are most diverse at the equator and their diversity declines toward the poles....
wing, and provide coloration. Scales are quite common and have evolved multiple times

Convergent evolution

Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action....
with varying structure and function.

Scales are generally classified as part of an organism's integumentary system

Integumentary system

The integumentary system is the organ system that protects the body from damage, comprising the skin and its appendages. The integumentary system has a variety of functions; it may serve to waterproof, cushion and protect the deeper tissues, excrete wastes, regulate temperature and is the location of receptors for pain, sensation, pressu...
.

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Fish scales

Fish scales are dermally derived, specifically in the mesoderm. This fact distinguishes them from reptile scales paleontologically. Genetically, the same genes involved in tooth and hair development in mammals are also involved in scale development.

Cosmoid scales

True cosmoid scales can only be found on the extinct Crossopterygians. The inner layer of the scale is made of lamellar bone. On top of this lies a layer of spongy or vascular

Blood vessel

The blood vessels are the part of the circulatory system that transport blood throughout the body. There are three major types of blood vessels: the artery, which carry the blood away from the heart, the capillary, which enable the actual exchange of water and chemicals between the blood and the tissues; and the veins, which carry blood from...
bone and then a layer of dentinelike material called cosmine. The upper surface is keratin

Keratin

Keratins are a family of fibrous protein; tough and insoluble, they form the hard but mineral structures found in reptiles, birds, amphibians and mammals....
. The coelacanth

Coelacanth

Coelacanth is the common name for an Order of fish that includes the oldest living Lineage of gnathostomata known to date. The coelacanths, which are related to lungfishes and tetrapods, were believed to have been extinction since the end of the Cretaceous period, until the first Latimeria specimen was found off the east coast of Sout...
has modified cosmoid scales that lack cosmine and are thinner than true cosmoid scales.

Ganoid scales

Ganoid scales can be found on gar

Gar

In American English the name gar is strictly applied to members of the Lepisosteus, a family including seven living species of fish in two genera that inhabit fresh, brackish, and occasionally marine, waters of eastern North America, Central America, and the Caribbean islands....
s (family Lepisosteidae) and bichir

Bichir

The bichirs are a family, Polypteridae, of archaic-looking Actinopterygii, the sole family in the order Polypteriformes.All species occur in freshwater habitats in tropical Africa and the Nile River system, mainly swampy, shallow floodplains and estuary....
s and reedfishes (family Polypteridae). Ganoid scales are similar to cosmoid scales, but a layer of ganoin lies over the cosmine layer and under the enamel. They are diamond-shaped, shiny, and hard.

Placoid scales

Placoid scales are found on cartilaginous

Cartilage

Cartilage is a type of dense connective tissue. It is composed of specialized cells called chondrocyte that produce a large amount of extracellular matrix composed of collagen fibers, abundant ground substance rich in proteoglycan, and elastin fibers....
fish including shark

Shark

Sharks are a type of fish with a full Cartilage skeleton and a highly Streamlines, streaklines and pathlinesd body. They respire with the use of five to seven gill slits....
s. These scales, also called denticles, are similar in structure to teeth

Tooth

Teeth are small whitish structures found in the jaws of many vertebrates that are used to tear, scrape, and chew food. Some animals, particularly carnivores, also use teeth for hunting or defense....
.

Leptoid scales

Leptoid scales are found on higher order bony fish and come in two forms, ctenoid and cycloid scales.

As they grow, cycloid and ctenoid scales add concentric layers. The scales of bony fishes are laid so as to overlap in a head-to-tail direction, a little like roof tiles, allowing a smoother flow of water over the body and therefore reducing drag

Drag (physics)

The term drag is widely used in Physics and Engineering and is central to the field of fluid dynamics. "Drag" refers to forces that oppose the motion of a solid object through a fluid ....
.

Cycloid scales

Cycloid scales have a smooth outer edge, and are most common on more primitive fish with soft fin rays, such as salmon

Salmon

Salmon is the common name for several species of fish of the family Salmonidae. Several other fish in the family are called trout,the difference is often attributed to the migratory life of the salmon as compared to the residential behaviour of trout, this holds true for the Atlantic salmon....
and carp

Carp

Carp is a common name for various freshwater fish of the family Cyprinidae, a very large group of fish originally from Eurasia and southeast Asia....
.

Ctenoid scales

Ctenoid scales have a toothed outer edge, and are usually found on more derived fishes with spiny fin rays, such as bass

Bass (fish)

Bass is a name shared by many different species of popular gamefish. The term encompasses both fresh water and sea water species. All belong to the large order Perciformes, or perch-like fishes, and in fact the word bass comes from Middle English bars, meaning "perch." These are some of the best known species of bass:...
and crappie

Crappie

Pomoxis is a genus of freshwater fish in the sunfish family of order Perciformes. The type species is P. annularis, the white crappie....
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Reptilian scales

Reptile

Reptiles, or members of the class Reptilia, are air-breathing, cold-blooded vertebrates that have skin covered in scale as opposed to hair or feathers....
scale types include: cycloid, granular (which appear bumpy), and keeled (which have a center ridge).

The scales of all reptiles have an epidermal component (what one sees on the surface), but many lizards have osteoderms underlying the epidermal scale, as do crocodilians and turtles. Snakes, tuataras and many lizards lack osteoderms. All reptilian scales have a dermal papilla underlying the epidermal part, and it is there that the osteoderms, if present, would be formed.

Arthropod scales

Butterflies and moth

Moth

A moth is an insect closely related to the butterfly, both being of the Order Lepidoptera. The differences between butterflies and moths are more than just taxonomy....
s - the order Lepidoptera

Lepidoptera

Greek language

Greek is an Indo-European languages native to the southern Balkan peninsula, the language of the Greek people. It forms an independent branch within Indo-European....
"scale-winged") - have membranous wings covered in delicate, powdery scales, which are modified setae. Each scale consists of a series of tiny stacked platelets of organic material, and butterflies tend to have the scales broad and flattened, while moths tend to have the scales narrower and more hair-like. Scales are usually pigment

Pigment

A pigment is a material that changes the color of light it Reflection as the result of selective color absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which the material itself emits light....
ed, but some types of scales are metallic, or iridescent, without pigments; because the thickness of the platelets is on the same order as the wavelength

Wavelength

In physics, wavelength is the distance between repeating units of a propagating wave of a given frequency. It is commonly designated by the Greek language letter lambda ....
of visible light the plates lead to structural coloration and iridescence

Iridescence

Iridescence is an optical phenomenon in which hue changes with the angle from which a surface is viewed. Iridescence may be easily seen in soap bubbles and butterfly wings....
through the physical phenomenon described as thin-film optics

Thin-film optics

Thin-film optics is the branch of optics that deals with very thin structured layers of different materials. In order to exhibit thin-film optics, the thickness of the layers of material must be on the order of the wavelengths of visible light ....
. The most common color produced in this fashion is blue

Blue

Blue is a colour, the perception of which is evoked by light having a spectrum dominated by energy with a wavelength of roughly 440?490 Nanometre....
, such as in the Morpho butterflies. Other colors can be seen on the Sunset moth.

Scale (zoology)

Fish scales

Cosmoid scales

Ganoid scales

Placoid scales

Leptoid scales

Cycloid scales

Ctenoid scales

Reptilian scales

Arthropod scales

Bibliography