These dermal cells form a papilla that grows upwards and pushes the Malpighian layer to form an arch-like structure. The development of a placoid scales begins with an increase in the number of dermal cells accumulated at different points in the stratum germinativam (Malpighian layer). The fork is made up of dentin with an enamel coating on the outside. Thorny structures are inserted into the dermis with the help of sharp`s fibers and other fibers. Each base plate is made up of calcium-rich tissues.
Circuli in fish skin#
As a result, the scales protect the skin from abrasive injuries. At the bottom of each scales is a base plate and a pointed thorn arising from the base. Placoid scales are arranged in different rows individually to form the outer skeleton. The scales cover the skin like sand grains. Such scales are found only in cartilaginous fish (Chondrichthyes) but are absent in the subclass Holocephali. The following is a description of the different types of scales: Placoid Scales There are three types of non-placid scales, namely:īony ridge scales are divided into cycloid and ctenoid based on the thorns. Types of Scalesįish scales can be divided into four based on shape, namely:įish scales can also be divided into two based on their structure, namely: The age of the fish is determined by counting the number of annulus in scales. In that densely enclosed region a black circle is formed which is known as the annulus. Circulus formed in summer are quite wide whereas circulus formed in winter are intertwined. A small circular growth ring is formed in the scales and this ring is called circuli or circulus (in singular). However, the number of scales remains the same throughout life but the lost scales can be restored at some point. When the fish hatches from the egg, its body is covered by small scales. The scales form a lateral line in the body of the fish along the side of the body and play an important role in detecting vibrations in the water as it acts as a sensory receptor. The scales contain a variety of pigments that give the fish a variety of colors. Scales cover most of the body and protect the skin from injury. Other fish such as trout and freshwater eel have very small scales. Some fish, especially paddle fish ( Polyodon), mirror carp ( Cyprinus carpio) have partial scales. These cells secrete mucus or slime, which prevents parasites, fungi, pathogens, etc. The epidermis contains numerous mucus cells. The scales develop as external growths of the epidermis or skin. The body of an ideal fish is covered by thin scales. The outer skeleton of a fish is called scales. Such scales are made up of small, thin, thorny and crushed or bony plates that stick closely to each other. Afterwards, dermal scales emerge from the mesenchyme of fish. Such scales are found in terrestrial vertebrates such as reptiles, birds and mammals. Epidermal scales originate from the malpighian layer of the epidermis. The skeletons of many vertebrates are covered by two types of scales, namely epidermal and dermal. Scales are small plate-shaped dermal or epidermal structures that are found in the outer skeletons of fish, reptiles, or some mammals.
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