The clams, mussels, tube worms, and other creatures at the vent have a symbiotic relationship with bacteria. The giant tube worms, for example, have no digestive system-no mouth or gut. The worm depends virtually solely on the bacteria for its nutrition, says microbial ecologist Colleen M. Cavanaugh of Harvard University. Both partners benefit.
The brown, spongy tissue filling the inside of a tube worm is packed with bacteria-about 285 billion bacteria per ounce of tissue. Its essentially a bacterial culture, says Cavanaugh.
The plumes at the top of the worms body are red because they are filled with blood, which contains hemoglobin that binds hydrogen sulfide and transports it to the bacteria housed inside the worm. In return the bacteria oxidize the hydrogen sulfide and convert carbon dioxide into carbon compounds that nourish the worm.
Tube worms reproduce by spawning: They release sperm and eggs, which combine in the water to create a new worm. Biologists dont know how the infant worm acquires its own bacteria. Perhaps the egg comes with a starter set.
Scientists also dont know how tube worms and other organisms locate new vents for colonization . The vents are small, and theyre separated, like island, says Cindy Lee Van Dover, a biologist and Alvin pilot who studies vent life. Most vent organisms have a free-swimming larval stage. But scientists arent sure whether the larvae float aimlessly or purposely follow clues-such as chemical traces in the water-to find new homes.
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2016-02-26
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