Morphology of a tube worm hosting sulphide-oxidizing symbionts

Description

Tube worms host their symbionts in the trophosome, a specialized organ. Oxygen (O2), sulphide (HS–), and carbon dioxide (CO2) are taken up from the surrounding water through the animal’s plume and delivered via the blood stream to the symbionts. Clams harbour their symbionts in their gills. Oxygen and carbon dioxide are available from the surrounding water, and sulphide is taken up from the sediment through the clam’s foot.