Which giant tube worm lives around deep-sea hydrothermal vents without a digestive tract?

The giant tube worm that lives around deep-sea hydrothermal vents without a digestive tract is Riftia pachyptila.

Riftia pachyptila can grow to roughly two metres and forms dense colonies near vents in the eastern Pacific. Its red plume absorbs oxygen, carbon dioxide, and hydrogen sulfide from the surrounding water. The worm does not eat in the ordinary sense; instead, bacteria living inside a specialized organ called the trophosome use chemical energy to make organic nutrients.

This partnership is an example of chemosynthesis-based symbiosis. Hydrothermal vents lack sunlight, so their communities are powered by chemical reactions rather than photosynthesis. Young worms initially have a mouth and gut, but these structures disappear as the symbiotic lifestyle develops. The sulfur used by the bacteria is toxic to many animals, yet the worm’s circulatory system transports it safely to the internal symbionts.