The body of a fish has different fish plans and there are multiple types of fish bones. Thus, there is no typical skeleton of a fish though broadly it can be divided into a head, trunk and a tail. It is also important to know that types of fish bones can primarily be distinguished between vertebrates (those which have bones) and invertebrates (those which do not have bones). It is interesting to know that the fish are the first vertebrates. The evolution of bones began with the fish. Bone is the tissue that gives support to the skeleton (internal or external) of vertebrates.
After dividing the fish into vertebrates and invertebrates, the types of fish bones is divided further. The bone of early vertebrates was of two types- cellular and acellular. The only difference lies in the fact that cellular bone has spaces for osteocytes, the cells that form the bone. The skeleton of the earliest fish is formed of bone, thus giving it the name- dermal bone. Dermal bone constitutes all the visible bones of the head and the trunk. It also composes the scales and biting surfaces inside the mouth of the fish. There are other types of specific bones too which developed. The main characteristic of these bones were the complexity, composition and nature of the external layers of the dermal bones. The growth process too becomes an important factor. The types of fish bones do not end here. There is another. Perichondral bone is mostly found surrounding soft tissue that passes through the cartilage. Another is the Endochondral bone which constitutes most of the internal skeleton.
Fish by nature are vertebrates. There is a basic built of the fish- a rod running through the entire body of the fish. The rod is stiff in nature. There is a hollow tube of nervous tissue. The mouth is located at or below the anterior end, while the anus at the exterior, before the body ends. The vertebral column consists of the spine of the vertebra with projections. The centrum/ central body/spine of the vertebra is usually concave at the ends. This restricts the movement of the fish. It is interesting to note that the vertebrae of lobe-finned fishes have three discrete elements of its body. The spinal cord is surrounded by vertebral arch. Beneath it lies a small plate that protects the upper surface of the fish and beneath lies a larger arch-shaped plate that protects the lower border. Further, in most ray-finned fishes, such structures are combined. In sharks which are cartilaginous fish, the vertebrae consist of cartilageous tubes which are two in number. Hagfishes are left bereft of a true vertebral column, thus excluding themselves from the proper category of a vertebrate. They possess a cranium, thus sometime they fall in this category. The Lampreys are known to have vertebral arches which are discontinuous in nature.
Thus, the different types of fish bones help us understand their anatomy. These water creatures are beautiful in form and pattern and delving deep into a study of their types of fish bones makes for an interesting read!