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Resembling giant lipsticks, giant 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) tall. 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 billions of bacteria that live inside them. These bacteria convert the chemicals spewing out of the vents into worm food. This chemical-based food-making process is known as chemosynthesis.
The bright-red plume is the tubeworm's breathing apparatus. The blood in it contains special forms of hemoglobin that have a super-high affinity for the oxygen in the seawater. Masses of tubeworms, with their showy plumes, inspired scientists to name one vent field "The Rose Garden" in 1979.
However, during an expedition that began in May 2002, scientists from Woods Hole Oceanographic Institution and NOAA's Ocean Exploration Program discovered that "The Rose Garden" had been paved over by erupting lava. However, they did find the genesis of a new site nearby, populated with tiny tubeworms and other life. They aptly named the site "Rosebud."
When tubeworm larvae settle down at new vent sites, they grow rapidly and reproduce because when a vent shuts down, these animals cannot survive. As the flow of vent fluids ceases, the organisms that depend on the vents chill and starve. While tubeworms and other sessile organisms that are "rooted" to the seafloor die, it's possible that fish and crabs may move on to other vent sites.
Click here for a closer look at a tubeworm.
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Dr. Monika Bright, a professor at the University of Vienna, Austria, decided that the deep sea was where she wanted to focus her research after her first dive in the submersible Alvin in 1992.
"I got hooked on the giant tubeworms," she says.
These worms without eyes, mouth, or gut (stomach) survive thanks to a mutually beneficial partnership -- a symbiotic relationship -- with billions of bacteria that live inside them. The worm provides the bacteria with a home, and the bacteria convert the toxic chemicals that spew out of the vents into worm food.
Yet no one knew how and when the tubeworms acquired their bacteria until she and her colleagues recently solved the mystery.
"The tubeworms depend entirely on their symbionts and yet they don't pass them on to their offspring. Why not? -- For me, this was always an intriguing question," she notes. "Knowing the mechanism of transmission will not only give us insight into the evolution of this deep-sea association but also the evolution of symbiosis in general."
During Extreme 2004, Dr. Bright and her colleagues sought to determine how and when the bacteria take up residence in the worm. They collected baby tubeworms in Vestimentiferan Artificial Settlement Devices (VASDs) deployed in a vent field and then studied the organisms in the lab.
In May 2008, the researchers reported their results in the scientific journal Nature.
The team showed that the bacteria enter the tubeworm larvae through a skin infection. They then crawl inward to tissues which they induce to form the tubeworm's trophosome. Here, they take up permanent residence, sustaining the tubeworm in return for a steady food supply and a safe home.
Dr. Bright shared the Extreme 2004 expedition with students in Austria using University of Delaware materials translated into German. Her research was funded by the Austrian Science Foundation.
