All sharks are carnivorous and many people believe that sharks will eat just about anything; for a few species, such as the tiger shark, this is true. The vast majority of sharks, however, are far more specialised for particular prey items, and rarely stray from these. Some of the most specialised sharks have developed a filter feeding technique, which is employed by the whale, basking and megamouth sharks. These three shark species have evolved plankton feeding independently and use different strategies. Whale sharks feed using suction to take in large concentrations of plankton and small fishes. Basking sharks are ram-feeders, swimming steadily, with their mouth wide open, through plankton blooms. Megamouth sharks may make their suction feeding extra efficient with the use of luminescent tissue inside the mouth the attract prey in the deep ocean. This type of feeding was only possible through the evolution of gill rakers, long slender filaments that form a very efficient sieve, analogous to the baleen plates of the great whales. Plankton is trapped in these filaments and swallowed from time to time in huge mouthfuls. Teeth in these species are very small compared to the size of the animal, because they are not needed for feeding.

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