Caption: Goby fish scales and skin (Awaous guamensis). Fish scales are dermally derived, specifically in the mesoderm. This fact distinguishes them from reptile scales. Scales are the overlapping series of hard plates that cover a fish's body. Scales serve to protect the body from the outside dangers such as predators and infection. Not all fish share the same kind of scales. There are four main types of scales: placoid, ganoid, ctenoid, and cycloid. Fish scales are covered with fish skin, a fine layer of epithelial cells. Fish skin like many other vertebrates (amphibians, reptiles, birds, mammals) consists of two principal layers - superficial epidermis and deeper dermis. The epidermis consists of two or more layers. The deepest is a series of closely packed, discrete cells called the germinal layer, or stratum germinativum. The outer epidermal cells are formed from the germinal layer. Body fish slimes are produced by epidermal cells and their degradation. Epidermal cells can have highly convoluted surfaces that retain slime, which has a primary function of protection from pathogens and parasites.
Magnification*: x24
Type: SEM
Copyright 2009 Dennis Kunkel Microscopy, Inc.
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