Anatomy of finfish and shellfish

UNIT 1 - Anatomy of Fin Fish

1.1 External Anatomy of Finfish
Anatomically (Biologically) speaking a fish is composed of ten systems of bodily organs that work together to make up the whole individual. These ten systems cover the fish, handle its food, carry away wastes, they integrate the life processes of the fish and relate it to conditions in the environment. They also provide for breathing and for protections against injury. They support the body and enable movement and finally they work to perpetuate fish as species and through evaluation, as a major group of animals.

The living species of fish are usually divided into three classes: the Agnatha, the jawless fishes, comprising the hagfishes and lampreys; the Chondrichthyes, the cartilaginous-skeleton fishes, such as sharks and rays; and the Osteichthyes, the bony-skeleton fishes, comprising all other living fishes. The skeletons of these three groups vary in fundamental ways. In the hagfishes and lampreys the backbone is basically a notochord, a rod like structure composed of unique notochordal tissue. In sharks and rays the notochord is surrounded and constructed by spaced rings of cartilage, the vertebrae, to form a backbone.