By Brent Privett
Geographic Range
Riftia pachyptila lives on the ocean floor near hydrothermal vents on the East Pacific Rise, more than a mile under the sea (Cary et al. 1989).
Biogeographic Regions:
pacific ocean 
(native ).
Habitat
R. pachyptila lives in sulfide rich environments along hydrothermal vents on the ocean floor (Black et al. 1997, Univ. of Delware Marine Studies. 2000).
Aquatic Biomes:
benthic ; oceanic vent .
Physical Description
An adult R. pachyptila has a tough chitonous tube that grows to over 3 meters tall. At the top of the tube is a large red plume containing hemoglobin that gives R. pachyptila the appearence of a giant paintbrush . Inside the tube, the worm's body is colorless, and holds a large sack called a trophosome (along with its other organs). This sack contains billions of symbiotic bacteria that make food for the worm. The worm has no mouth, eyes, or stomach (Cary et al. 1989; Univ. of Delware Marine Studies 2000).
Reproduction
Females release lipid rich eggs which float slowly upward. Males release sperm bundles that contain hundreds of sperm cells. The sperm bundles then swim up to meet the eggs where they are fertilized. The larval worms swim down near the hydrothermal vents and attach to the cooled lava where they grow to form new tube worm communities. (Cary et al. 1989, Univ. of Delware Marine Studies 2000)
Behavior
Larval R. pachyptila drift in the deep water, trying to find a hydrothermal vent that they can live near. They will settle down and attach to the rocky bottom when they detect the right chemicals in the water.
Food Habits
R. pachyptila depends on a symbiotic relationship with chemosynthetic bacteria for its food. Although it has no mouth or gut it is born with a mouth through which the bacteria enter. The tube worm uses a feeding sac (called a trophosome) to gather sulfuric chemicals that the bacteria uses to make food for the worm. (Univ. of Delware Marine Studies 2000)
Economic Importance for Humans: Negative
Unknown.
Economic Importance for Humans: Positive
Unknown.
Conservation Status
IUCN Red List: [link]:
Not Evaluated.
US Federal List: [link]:
No special status.
CITES: [link]:
No special status.
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Other Comments
The taxonomic status of this strange group of worms is still being determined. There are several different scientific opinions about which group the species belongs to (Pearse et al. 1987; Black et al. 1997).
Contributors
Brent Privett (author), Fresno City College.
Jerry Kirkhart (editor), Fresno City College.
