In many vertebrates, the exoskeletal covering of body is made of two types of scales- epidermal and dermal. Epidermal scales are cornified derivatives of the Malpighian layer of epidermis. They are well developed in terrestrial vertebrates such as reptiles, birds and mammals. Dermal scales are mesenchymal in origin and especially developed in the fishes. They are small, thin, cornified, calcareous [...]
The air-bladder or swim-bladder is more or less a sac-like structure lying between the alimentary canal and the kidneys. It is a characteristic organ of Osteichthyes (bony fishes). It is a gas-filled pneumatic sac, called air-bladder or swim-bladder. Air-bladder does not occur in elasmobranchs. However, it is found in all Osteichthyes (bony fishes) except a few bottom dwellers (Lophius, Pleuronectes, [...]
In this article we will discuss about the fin system of fishes with the help of suitable diagrams. Fins: Fins are the chief organs of locomotion in fishes. These are either folds of skin or projections from the body surface. The fins are supported by fin-rays. These supporting rays may be bony, cartilaginous, fibrous or horny. There are mainly two [...]