Most Osteichthyes have a swim bladder that allows them to be weightless in water, as the gas filled or emptied to control the depth at which they occur. Fit better in the movement of ascent or descent fins sticking to the body and preventing friction. The fins are retained, however, because they are useful for more precise movements. In addition, the wings have evolved into different functions, as used to walk on the bottom (Periophthalmus Koelreuteria) to feel (Trigla, Trigla) and suckers (Lepadogaster), or wings for a time to jump above the surface ( Cheilopogon) avoiding aquatic predators in stressful situations. The typical morphology of the fish is the least hydrodynamic resistance offered for swimming: the sharp front end and a height equal to one quarter of body length, while the maximum height in the first third of the body count from the head. This form allows you to minimize turbulence facilitating progress.However, not all fish have a morphology similar to that described. The length varies from animal to other groups as well as propelling the movement. The driving part anguiliformes have a very elongated, the carangiform are intermediate and the most typical, and the propelling ostraciformes have a very small part. These different ways correspond to different and varied forms of fish life. Among the highlights carangiform a panel, the escombriformes, which is the type of motion is better suited to a continuous swimming. I have tuna, bonito, mackerel. They have a very muscular body with very low resistance to water: the tail is as thin as possible, lunate and rigid, and have pinnules that serve to reduce turbulence. Are therefore very hydrodynamic, enhancing the trait with a pointed face and grooves that allow even and odd fins withdraw and not offer resistance to movement.In order to have a high muscle activity, maintain body temperature above the middle, so they are said pseudohomeotermos. The big guys keep speeds of 60-70 km / h and top speed in excess of 100 km / h.