Convict cichlid fish scales, SEM

Scanning electron micrograph (SEM) convict cichlid fish scales and skin (Cichlasoma nigrofasciatum). Fish scales are dermally derived, specifically in the mesoderm. This fact distinguishes them from reptile scales. Scales protect the body from outside dangers such as predators and infection. Fish scales are covered with fish skin, a fine layer of epithelial cells. Fish skin like many other vertebrates 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. Epidermal cells can have highly convoluted surfaces that retain slime, which has a primary function of protection from pathogens and parasites. Magnification: x24 when shortest axis printed at 25 millimetres.