Resembling giant lipsticks, tubeworms (Riftia pachyptila) live over a mile deep on the Pacific Ocean floor near hydrothermal vents. They may grow to about 3 meters (8 ft) long. The worms' white tube home is made of a tough, natural material called chitin (pronounced "kite-in"). Tubeworms have no mouth, eyes, or stomach ("gut"). Their survival depends on a symbiotic relationship with the billions of bacteria that live inside of them. These bacteria convert the chemicals that shoot out of the hydrothermal vents into food for the worm. This chemical- based food-making process is referred to as chemosynthesis. Since a tubeworm has no mouth, how do bacteria enter the worm? Scientists have found that, during its earliest stages, the tubeworm does have a mouth and gut for bacteria to enter. But as the worm grows, these features disappear! While the tubeworm depends on the bacteria that live in its body for energy and food, sometimes tubeworms provide food for other deep-sea dwellers. Fish and crabs may nibble off the tubeworm's red plume.