SHARKS: TRUE OR FALSE

Sharks are more than teeth machines, swimming appetites and underwater noses. In fact, sharks come in all varieties. Some sharks are scary but some aren't scary at all. And some sharks would almost make you laugh. Some are small, slow and spotted. Sharks come in 350 varieties or species. Thirty species are considered dangerous. Even so, more people die each year from bee stings than from shark bites.The largest sharks, the whale shark and the basking shark, don't have teeth for chewing.

An adult whale shark has over four thousand tiny little teeth, less than one-tenth of an inch long. Like some whales, they filter tiny shrimplike plankton from the water into their bite-less mouths. They are so easy-going that Cousteau divers used to "hop a ride" on a whale shark; nowadays, there are so many divers and so few whale sharks that we prefer to leave them in peace.
Some sharks are so well equipped for eating that they're all teeth. Shark skin, which feels like sandpaper, is actually many small teeth linked together. These teeth are called "dermal denticles." They are the shark's version of the scales that cover other fish. Inside their skin, sharks are different from most fish, too, because their skeleton is made up of cartilage, which is softer and more flexible than bone. Their only bones are their teeth but, wow! what teeth. Some sharks have five rows of teeth. When one tooth breaks, another tooth which was lying down right behind the broken one, pops up, ready to work.

Two-thirds of a shark's brain helps it to do only one thing--smell. If our sense of smell were as good as a shark's, we could tell what our friends across town were having for dinner. Sharks can smell some substances that are as diluted as one part odor to one billion parts of sea water.Sharks are also very, very sensitive to electrical fields. Every living body gives off a small electrical field around its body. This "force" around us all is a byproduct of all the energy we generate just by being alive. Sharks can detect these electrical fields more easily than most other animals because of special sensors on their snout called the "ampullae of Lorenzini."

Sharks have relatively few babies, between one and one hundred, and the baby sharks take up to 24 months to grow.  (Elephants only take 22 months!) Some shark babies grow in eggs inside leathery cases. Occasionally these packets of eggs  wash up onto the beach after a storm; they're called "mermaid's purses" because they look like old-fashioned coin purses.
Fish-eating sharks have an important job. In a roundabout way, they keep fish healthy. Sharks eat sick, injured or weak fish because they're easier to catch. This way, other fish don't get sick and weak fish don't reproduce, making more weak fish. It's an important job, but it doesn't make the shark too popular.
Like a dog, most sharks have their own way of "warning." A dog barks or growls to let you know that it's upset. It's giving you a chance to go away. Some sharks do the same thing. They can't bark but they put on a swimming show. When a gray reef shark is upset, it will arch its back, point its fins down and swim slowly, in a strange back-and-forth manner. This means, "You're making me nervous. Go away or I'll have to be very nasty." The shark probably prefers not to have to go to the trouble to do anything like chase or attack. Fine with us!