Fish Scales

The bodies of most tropical fish are covered with scales. The scales are composed of a hard bony substance and serve to protect the fish, reducing the chance of injury and infection. Covering the scales is a very thin layer of epidermal (skin) tissue that contains mucous cells. These cells produce the slime that we normally attribute to fish. The mucous coating not only protects the fish against injury and infection, but also helps the fish to swim more easily in the water, reducing friction between the body and the water.

The scales of a fish are actually translucent, like glass, and lack color. The vibrant colors of tropical fish come from specialized pigment cells called chromatophores in the deeper dermal layer of the skin. Fish that are clear, like the Glassfish, lack these pigment cells. The color of the fish depends on the types of chromatophores present. There are generally three types of chromatophores in fish: melanophores give fish the darker colors of black, brown and blue; xanthophores produce red, yellow, and orange; and iridophores reflect light, producing a silvery shine common to many fish.