Skin: Structure and Functions

• The skin forms an external covering of the body and performs various important functions in fish.
• The skin of fishes is quite firmly attached and is hard and rough and is composed of two layers: epidermis (outer layer) and dermis (inner layer).
• A thick basement membrane is present between the dermis and epidermis.
• The epidermis is ectodermal in origin and consists of several layers of flattened and moist cells that secrete mucous to make skin slimy and frictionless.
• The deepest layer (base layer) of ethe epidermis is made up of columnar cells, called stratum germinativum in which cells are always multiplying by mitotic division to replace the outer worn-out cells.
• The epidermis of fishes contains large mucous cells or becker’s cells (produce mucous) and chromatocytes (impart color in fish).
• The dermis is mesodermal in origin and is composed of connective tissues, blood vessels, nerves, lymph vessels, collagen fibers, and cutaneous sense organs.
• Fish typically have numerous individual mucus-secreting skin cells that aid in insulation and protection, but may also have poison glands, photophores, or cells that produce a more watery, serous fluid.