Scale (anatomy)

In most biological nomenclature, a scale (lepís; squāma) is a small rigid plate that grows out of an animal's skin to provide protection. In lepidopteran (butterfly and moth) species, scales are plates on the surface of the insect wing, and provide coloration. Scales are quite common and have evolved multiple times through convergent evolution, with varying structure and function. Scales are generally classified as part of an organism's integumentary system. There are various types of scales according to shape and to class of animal. Fish scale File:Ganoid scales.png|Ganoid scales on a [[carboniferous]] fish ''[[Amblypterus]] striatus'' File:Denticules cutanés du requin citron Negaprion brevirostris vus au microscope électronique à balayage.jpg|Placoid scales on a [[lemon shark]] (''Negaprion brevirostris'') File:RutilusRutilusScalesLateralLine.JPG|Cycloid scales on a [[common roach]] (''Rutilus rutilus'') 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. True cosmoid scales can only be found on the Sarcopterygians. The inner layer of the scale is made of lamellar bone. On top of this lies a layer of spongy or vascular bone and then a layer of dentine-like material called cosmine. The upper surface is keratin. The coelacanth has modified cosmoid scales that lack cosmine and are thinner than true cosmoid scales. Ganoid scales can be found on gars (family Lepisosteidae), bichirs, 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. Ganoin scales are diamond shaped, shiny, and hard. Within the ganoin are guanine compounds, iridescent derivatives of guanine found in a DNA molecule. The iridescent property of these chemicals provide the ganoin its shine. Placoid scales are found on cartilaginous fish including sharks and stingrays.

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Fish scale

A fish scale is a small rigid plate that grows out of the skin of a fish. The skin of most jawed fishes is covered with these protective scales, which can also provide effective camouflage through the use of reflection and colouration, as well as possible hydrodynamic advantages. The term scale derives from the Old French escale, meaning a shell pod or husk. 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.

Keratin

Keratin (ˈkɛrətɪn) is one of a family of structural fibrous proteins also known as scleroproteins. Alpha-keratin (α-keratin) is a type of keratin found in vertebrates. It is the key structural material making up scales, hair, nails, feathers, horns, claws, hooves, and the outer layer of skin among vertebrates. Keratin also protects epithelial cells from damage or stress. Keratin is extremely insoluble in water and organic solvents.

Biology

Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary information encoded in genes, which can be transmitted to future generations. Another major theme is evolution, which explains the unity and diversity of life. Energy processing is also important to life as it allows organisms to move, grow, and reproduce.

Intrinsically High Capacity of Animal Cells From a Symbiotic Cnidarian to Deal With Pro-Oxidative Conditions

Gaëlle Delphine Toullec

The cnidarian-dinoflagellate symbiosis is a mutualistic intracellular association based on the photosynthetic activity of the endosymbiont. This relationship involves significant constraints and requires co-evolution processes, such as an extensive capacit ...

FRONTIERS MEDIA SA2022

Quantification of chemical toxicity in small-scale bioassays is challenging owing to small volumes used and extensive analytical resource needs. Yet, relying on nominal concentrations for effect determination maybe erroneous because loss processes can sign ...

NATURE RESEARCH2021

Legacy and alternative halogenated flame retardants in Lake Geneva fish

Legacy (i.e., polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCDD)) and alternative halogenated flame retardants (HFRs) were analyzed in 31 whole fish samples from Lake Geneva in 2018. Two fish species, namely, the burbot (Lota lota) a ...

2020