The Shark is a group of fish (Selordimorpha superordo) with a complete cartilage frame and a slender body. They breathe by using five gills (sometimes six or seven, depending on the species) on the side, or starting slightly behind, his head. Sharks have dermal-coated skin denticles to protect their skin from damage, from parasites, and to increase water dynamics. They have several replacement rows of teeth.
Sharks include species the size of a palm. The pygmy shark, Euprotomicrus bispinatus, a species of deep sea that is only 22 cm long, to whale sharks, Rhincodon typus, the largest fish capable of growing up to about 12 meters and which, like a whale, takes only plankton through a filter in his mouth. The bull shark, Carcharhinus leucas, is the most famous of several species that swim in both seawater and fresh water (this species is found in Lake Nicaragua, in Central America) and in deltas.