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Fish Anatomy All fish are animals that are cold-blooded, have fins and a backbone. The majority of fish have scales and breathe with gills. There are over 22,000 species of fish that began to evolve around 480 million years ago.
The following illustration of a Paradise Fish (Macropodus opercularis) shows some of the common external features of the fish. Fish skin: Fish skin consists of three layers: the epidermis on the outside, the dermis, and the hypodermis or underskin. The dermis contains the scales, which grow out of it and are attached more or less firmly. Large numbers of pigment cells (chromatophores) are present in the dermis. |
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External Anatomy
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These cells often are provided with long branches or processes and contain large numbers of tiny pigment granules that can be moved about in the cell plasma upon neural stimulus. When a stimulus occurs, the granules concentrate themselves at one point in the cell and the color appears diluted. If no other stimuli occur, the granules distribute themselves uniformly throughout the cell plasma and the color reappears. If the color-controlling nerve to one part of the body is crushed or clamped off, coloration becomes very intense in that part of the body.
The epidermis, which covers the scales and pigment cells, consists of two or more cell layers in which are found many slime-producing secretory cells. |
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