Shark skin is sometimes used as sandpaper. Water flows out of the gill slits after passing over their gills. The largest pelagic sharks are filter-feeders. These sharks strain small fishes, krill, larvae and other types of plankton out of the water. They eat huge quantities of tiny animals.
Sharks are internal fertilizers.
That means their eggs are fertilized in the female's body. Sperm travels along a groove on the clasper into the female's body. Some sharks lay egg-filled cases on the bottom of the ocean, called devil s wheelbarrows or mermaid s purses. The gestation period in sharks varies with each species. It ranges from nine months to as long as 22 months in spiny dogfish.