Sharks are amazing fish that have been around since long before the dinosaurs existed. They live in waters all over the world, in every ocean, and even in some rivers and lakes. Unlike bony fish, sharks have no bones ; their skeleton is made of cartilage, which is a tough, fibrous substance, not nearly as hard as bone. Sharks also have no swim bladder (unlike bony fish).
The biggest shark is the whale shark ( Rhincodon or Rhiniodon typus ), which can be up to 50 feet (15 m) long. It is a filter feeder and sieves enormous amounts of plankton to eat through its gills as it swims. It is also the biggest fish. The second biggest fish and shark is the basking shark ( Cetorhinus maximus ) which is about 40 feet (12.3 m) long and is another filter feeder. The biggest meat-eating sharks are the Greenland shark and the Great white shark ( Carcharodon carcharias ) which grow to be up to 21 feet (6.4 m) long. Great whites up to 37 feet (11.3 m) long have been reported, but not verified.
The largest shark known was the Megalodon ( Carcharodon or Carcharocles megalodon ) ; it is now extinct. It was an ancient, meat-eating shark that lived between 25 million and 1.6 million years ago. It was up to 40 feet (12 m) long and its teeth were each the size of a person's hand!
The oceanic white-tipped sharks are the most fearless predators. Jacques-Yves Cousteau says that it is: "the only species of shark that is never frightened by the approach of a diver, and they are the most dangerous of all sharks."
The fastest swimming sharks are the mako sharks and blue sharks, which can even leap out of the water. They are also among the fastest fish. Estimates of their speed varies; some say that they can swim at about 60 miles per hour (97 kph), while more conservative estimates are about 22 mph (35 kph). There hasn't been enough observation of their speeds to have a definitive answer.
The whale shark was long thought to be oviparous (an egg 14 inches (36 cm) long was found in the Gulf of Mexico in 1953; this would be the largest egg in the world). Recently, pregnant females have been found containing hundreds of pups. Whale sharks are viviparous , giving birth to live young. Newborns are over 2 feet (60 cm) long.
One Blue shark was found with 135 pups in her uterus.
Great White Shark Information TEETH TO SPARE A great white loses and replaces thousands of its teeth during its lifetime. Its upper jaw is lined with 26 front-row teeth; its lower jaw has 24. Behind these razor-sharp points are many rows of replacement teeth. The “spares” move to the front whenever the shark loses a tooth. At any one time about one-third of a shark’s teeth are in the replacement stage. HEADS UP Great whites are the only sharks that can hold their heads up out of the water. This ability allows them to look for potential prey at the surface. Great white sharks usually attack from underneath, surprising their unwary prey
Great white sharks can sprint through the water at speeds of 43 miles an hour (69 kilometers an hour). That’s about 8.5 times as fast as the top Olympic swimmer.
Scientists on the California coast tracked one shark as it swam all the way to Hawaii—2,400 miles (3,862 kilometers)—in only 40 days!
Unlike most fish, great white sharks’ bodies are warmer than their surroundings.
The sharks’ bodies can be as much as 27.3°F (15.17°C) warmer than the water the fish swim in. A higher temperature helps the great white shark swim faster and digest its food more efficiently.
SPEEDY SWIMMERS & HOT ON THE TRAIL
A pregnant female great white shark can carry as many as 14 babies in her belly. At birth, a 5-foot-long (1.52-meter), 60-pound (22-kilogram) pup looks and acts like a miniature adult. Great whites average between 10 and 15 feet (3 and 4.6 meters) long. Females tend to be bigger than males. The longest confirmed great white shark measured 19.5 feet (5.9 meters). Male or female, they’re the world’s largest meat-eating fish. A great white shark isn’t all white. A pale belly and dark charcoal-gray back help the shark avoid detection by prey. Viewed from above, the shark’s dark-colored back blends with the murky seafloor. From below, the shark’s belly matches the light-colored surface. Sneaky! BIG MAMA & SNEAK ATTACK
“ Man-eaters?” Maybe not. Some scientists believe that great white sharks are better described as “man-biters.” In more than half of all known great white attacks on swimmers, sharks have taken only a single bite before swimming away. Scientists speculate that perhaps people just don’t taste as good as seals or sea lions! NOT ON THE REGULAR MENU
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