Free Shark Screensaver

Shark Free Screensaver

Sharks are a type of fish with a full cartilaginous skeleton and a streamlined body. They respire with the use of five to seven gill slits. Sharks have a covering of dermal denticles to protect their skin from damage and parasites and to improve fluid dynamics; they also have replaceable teeth. Shark teeth are prized by collectors for their beauty, and because they are the only surviving relics of ancient sharks that are now extinct. Sharks range in size from the small pygmy shark, Euprotomicrus bispinatus, a deep sea species of only 22 centimetres (9 in) in length, to the whale shark, Rhincodon typus, the largest fish, which grows to a length of approximately 12 metres (39 ft) and which, like baleen whales, feeds only on plankton, squid, and small fish through filter feeding. The bull shark, Carcharhinus leucas, is the best known of several species to swim in both salt and fresh water and in deltas. The teeth of carnivorous sharks are not attached to the jaw, but embedded in the flesh, and in many species are constantly replaced throughout the shark s life; some sharks can lose 30,000 teeth in a lifetime. Studies on the behaviour of sharks have only recently been carried out leading to little information on the subject, although this is changing. The classic view of the shark is that of a solitary hunter, ranging the oceans in search of food; however, this is only true for a few species, with most living far more sedentary, benthic lives.