Fish is an aquatic organism which belongs to the subphylum Pisces. In the taxonomical hierarchy, fishes belong to the kingdom Animalia, phylum Chordata. They are in diverse groups which include jawless fish, armoured fish, cartilaginous fish, lobe-finned fishes and ray-finned fish and so on. Among these, most of them are ectothermic i.e. cold-blooded organisms. According to the behavior and characteristics nature, they show diversity in their bodily structures. Most of the fishes have strong and firm bony skeletal system.
Skeletal System of Fish
General features of fishes include fins, streamlines and scales and tails. But differences are highlighted under their skins. Hence classification is much easier based on the skeletal system. A variety of fishes is found in aquatic habitat some may be cartilaginous (Chondrichthyes) or bony fishes (Osteichthyes). The skeletal system of fishes is either composed of thin and flexible cartilage or hard calcified bones or both. They are good swimmers and their body structures are designed accordingly.
What does a skeletal system of fish constitutes?
A skeleton of fish consists of the vertebral column, jaw, ribs, cranium and intramuscular bones. It provides protection and control and also they produce red blood cells in addition to kidneys and spleen.Starting from the head, bony fish consist of solid hard bones called cranium. Cranium protects the brain from mechanical stresses. Osteichthyes have hinged jaws which aid them in feeding. But fishes like hagfish, lampreys are jawless fishes. Swim bladders help them to take up the dissolved oxygen from water and provides buoyancy. Otoliths are unique characteristics of ear plates of bony fish which helps in steadiness.
Gills are breathing organ for bony fishes. There are three pairs of bones that aid gills. These pair of bones is called gill arches which are made of bony filaments. Fins are a vital part of fish. They help for propulsion, steering, and stability. Paired fins take up the role of steering while caudal fins and dorsal fins help in propulsion and stability respectively.
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