The teeth of the sharks.Sharks have more than one row of teeth. Their teeth, which are not too solid, are being replaced all the time. The old teeth fall out easily. Predatory sharks grow new teeth every eight to fifteen days. Because a shark's bite is so powerful, the teeth break easily. Some sharks eat everything they see, for example metal objects, coke bottles, parts of bikes or cars, wood, and all the garbage that ships dump in the ocean. Other sharks prefer a very special menu: there are species that only eat octopuses, the pigshark (Heterodontus spp) only eats smoothsharks (Mustelus spp) and crustaceans. The weaselshark (Hemigaleus microstoma) only eats cephalopods, especially the eight-arm variety. Bigger sharks eat animals such as swordfish, marlins, dolphins and seals. The tigershark (Galeocerdo cuvieri) is an omnivorous sort, and can thus be dangerous for people. Young tiger sharks eat sea snakes in particular, older ones eat turtles and sea birds.
How the sharks get their food.Sharks have their own ways of getting food. Predatory sharks scoop out their prey, and the pigshark crushes its prey. The small Brazilian sucking- shark has a very special way of procuring its food: it has large suction lips, and affixes itself to a big fish or another shark. Then, with its teeth, it tears off a bit of flesh and eats it. Sometimes it fastens itself to a submarine. A sucking-shark sometimes emits light to lure its prey. A normal sucking-shark (Isistius plutodus) grows to 40 cm, but has teeth which are proportionately twice as big as the teeth of a great white shark. The basking shark, whale shark and bigmouthshark filter the water for small fish and plankton, like a whale does. Other sharks use different parts of their body for finding food. Foxsharks stun their prey by a blow of the tail. The tail is used as a sort of club. The sawshark, finally, kills its prey by a blow of its serrated jaw.