The integumentary system of fish consists of the skin and its derivatives, which include the scales, mucus, fins and glands. The skin serves many important functions, including protecting the fish from injury and infection, regulating body temperature, and allowing the fish to sense its environment.
Skin
The skin of fish is composed of two layers: the epidermis and the dermis. The epidermis is the outer layer and is made up of several layers of cells. The topmost layer of the epidermis is called the stratum corneum and is composed of dead cells that help to protect the fish from water loss and infection. The dermis is the inner layer of the skin and is made up of connective tissue, blood vessels and nerves. The dermis provides strength and support for the skin and also contains the skin glands.
Scales
Scales are found on the skin of most fish and provide protection from injury and infection. Scales are made of a variety of materials, including bone, cartilage and dentin. The type of scale varies among fish species. Some fish have scales that are embedded in the skin, while others have scales that are attached to the skin by a thin layer of connective tissue.
Mucus
Fish produce a slimy mucus that helps to protect their skin from water loss and infection. Mucus is also important for allowing fish to move easily through the water.
Fins
Fins are appendages that help fish to swim. Fins are made up of a thin membrane supported by bony or cartilaginous rays. The fins are attached to the body of the fish by a series of muscles that allow the fish to move the fins in different directions.
Glands
Fish have a variety of glands that secrete different substances. These glands include mucous glands, which produce mucus; venom glands, which produce poison; and pheromone glands, which produce chemicals that attract other fish.