How are sharks and rays different from other fishes?
• Sharks and rays do not have true bones like other fishes. They have cartilage instead which is lighter and much more elastic and allows them to bend in very tight circles. • Sharks do not have swim bladders. A swim bladder is a gas filled sack inside the body of bony fishes that allows them to stay still without sinking. Sharks compensate by having a very big liver that is filled with oil. Even so, sharks sink unless they keep swimming forward. The exception is the Sandtiger Shark which swallows air to make itself more buoyant. • A shark’s upper jaw is not fused to its skull like most animals. When a shark bites a large object, it is able to move its upper and lower jaw forward in order to take a bigger bite. • Unlike other fishes, sharks are able to replace their teeth constantly. New teeth grow from the inner surface of the jaw and rotate forward when the old teeth get worn out or lost during feeding. • Sharks and rays do not reproduce like other fishes. Most fish release clouds of
