Fish scale Wikipedia. The skin of most fishes are covered with scales, which, in many cases, are animal reflectors or produce animal coloration. Scales vary enormously in size, shape, structure, and extent, ranging from strong and rigid armour plates in fishes such as shrimpfishes and boxfishes, to microscopic or absent in fishes such as eels and anglerfishes. The morphology of a scale can be used to identify the species of fish it came from. Cartilaginous fishes sharks and rays are covered with placoid scales. Most bony fishes are covered with the cycloid scales of salmon and carp, or the ctenoid scales of perch, or the ganoid scales of sturgeons and gars. A cycloid is the curve traced by a point on the rim of a circular wheel as the wheel rolls along a straight line without slippage. A cycloid is a specific form of. ZERODAY This scene files have been broken into measure of the film as well as the opening and middle sections. If you are looking to just download the instrument. Want to thank TFD for its existence Tell a friend about us, add a link to this page, or visit the webmasters page for free fun content. Link to this page. China Pump manufacturers Select 2017 high quality Pump products in best price from certified Chinese Water Equipment manufacturers, Engine Pump suppliers. Download free evaluation copy One file, just run it. No install necessary. The free evaluation copy can do everything that the full version can do, but all output is. Looking for books on Classical Mechanics Check our section of free ebooks and guides on Classical Mechanics now This page contains list of freely available Ebooks. Some species are covered instead by scutes, and others have no outer covering on the skin. Fish scales are part of the fishs integumentary system, and are produced from the mesoderm layer of the dermis, which distinguishes them from reptile scales. The same genes involved in tooth and hair development in mammals are also involved in scale development. The placoid scales of cartilaginous fishes are also called dermal denticles and are structurally homologous with vertebrate teeth. It has been suggested that the scales of bony fishes are similar in structure to teeth, but they probably originate from different tissue. Most fish are also covered in a protective layer of mucus slime. Placoid scaleseditCartilaginous fishes, like this tiger shark, have placoid scales dermal denticles. SAT preparation that can be viewed online or downloaded for free. MP3 audio version also free. Cycloid circular scales have a smooth texture and are uniform, with a smooth outer edge or margin. They are most common on fish with soft fin rays, such as salmon. Placoid scales as viewed through an electron microscope. Also called dermal denticles, these are structurally homologous with vertebrate teeth. C396&ssl=1' alt='Free Download Cycloid ' title='Free Download Cycloid ' />Placoid scales are found in the cartilaginous fishes sharks, rays, and chimaeras. They are also called dermal denticles. Placoid scales are structurally homologous with vertebrateteeth denticle translates to small tooth, having a central pulp cavity supplied with blood vessels, surrounded by a conical layer of dentine, all of which sits on top of a rectangular basal plate that rests on the dermis. The outermost layer is composed of vitrodentine, a largely inorganic enamel like substance. Placoid scales cannot grow in size, but rather more scales are added as the fish increases in size. Similar scales can also be found under the head of the denticle herring. The amount of scale coverage is much less in rays and chimaeras. The skin of sharks is entirely covered by placoid scales. The scales are supported by spines, which feel rough when stroked in a backward direction, but when flattened by the forward movement of water, create tiny vortices that reduce hydrodynamic drag, making swimming both more efficient as well as quieter compared to that of bony fishes. The rough, sandpaper like texture of shark and ray skin, coupled with its toughness, has led it to be valued as a source of rawhide leather, called shagreen. One of the many historical applications of shark shagreen was in making hand grips for swords. Unlike bony fish, sharks have a complicated dermal corset made of flexible collagenousfibers arranged as a helical network surrounding their body. The corset works as an outer skeleton, providing attachment for their swimming muscles and thus saving energy. Their dermal teeth give them hydrodynamic advantages, as the scales reduce the turbulence of swimming. Leptoid scaleseditLeptoid scales are found on higher order bony fish, the teleosts the more derivedclade of ray finned fishes. As the fish grow, scales are added in concentric layers. The scales are arranged so as to overlap in a head to tail configuration, like roof tiles, allowing a smoother flow of water over the body and thereby reducing drag. Leptoid scales come in two forms cycloid and ctenoid. Cycloid scaleseditCycloid circular scales. The cycloid scale of a carp has a smooth outer edge. Cycloid circular scales have a smooth texture and are uniform, with a smooth outer edge or margin. They are most common on fish with soft fin rays, such as salmon and carp. Ctenoid scaleseditCtenoid toothed scales. The ctenoid scale of a perch has a toothed outer edge at top of image. Three ctenoid scales from various locations of a perch were stained. Significant variation can be observed between the medial middle of the fish, dorsal top, and caudal tail end scales. The ctentii of each of the scales is labeled. Ctenoid toothed scales are like cycloid scales, with small teeth along their outer edges. They are usually found on fishes with spiny fin rays, such as the perch like fishes. The scales have a rough texture with a toothed outer or posterior edge featuring tiny teeth called ctenii. These scales contain almost no bone, being composed of a surface layer containing hydroxyapatite and calcium carbonate and a deeper layer composed mostly of collagen. The enamel of the other scale types is reduced to superficial ridges and ctenii. Ctenoid scales, similar to other epidermal structures, originate from placodes and distinctive cellular differentiation makes them exclusive from other structures that arise from the integument. Development starts near the caudal fin, along the lateral line of the fish. The development process begins with an accumulation of fibroblasts between the epidermis and dermis. Collagen fibrils begin to organize themselves in the dermal layer, which leads to the initiation of mineralization. Suspense Thriller Movies Moana there. The circumference of the scales grows first, followed by thickness when overlapping layers mineralize together. Ctenoid scales can be further subdivided into three types Crenate scales, where the margin of the scale bears indentations and projections. Spinoid scales, where the scale bears spines that are continuous with the scale itself. True ctenoid scales, where the spines on the scale are distinct structures. Both cycloid and ctenoid scales are overlapping, making them more flexible than cosmoid and ganoid scales. Unlike ganoid scales, they grow in size through additions to the margin. The scales of some species exhibit bands of uneven seasonal growth called annuli singular annulus. These bands can be used to age the fish. Most ray finned fishes have ctenoid scales. Some species of flatfishes have ctenoid scales on the eyed side and cycloid scales on the blind side, while other species have ctenoid scales in males and cycloid scales in females. Ganoid scaleseditGanoid scales are found in the sturgeons, paddlefishes, gars, bowfin, and bichirs. They are derived from cosmoid scales, with a layer of dentine in the place of cosmine, and a layer of inorganic bone salt called ganoine in place of vitrodentine. Most are diamond shaped and connected by peg and socket joints. They are usually thick and have a minimal amount of overlap as compared to other scales. In sturgeons, the scales are greatly enlarged into armour plates along the sides and back, while in the bowfin the scales are greatly reduced in thickness to resemble cycloid scales see above. Elasmoid scaleseditElasmoid scales are thin, imbricated scales composed of a layer of dense, lamellar bone called isopedine, above which is a layer of tubercles usually composed of bone, as in Eusthenopteron. The layer of dentine that was present in the first sarcopterygians is usually reduced, as in the extant coelacanth, or entirely absent, as in extant lungfish and in the Devonian Eusthenopteron. Elasmoid scales have appeared several times over the course of fish evolution. They are present in some lobe finned fishes coelacanths, all extant and some extinct lungfishes, some tetrapodomorphs like Eusthenopteron, amiids, and teleosts, whose cycloid and ctenoid scales represent the least mineralized elasmoid scales. Cosmoid scaleseditCosmoid scales are found in several ancient lobe finned fishes, including some of the earliest lungfishes, and were probably derived from a fusion of placoid scales. They are composed of a layer of dense, lamellar bone called isopedine, above which is a layer of spongy bone supplied with blood vessels.