The Garden Without Sunlight: Tube Worms at the Deep-Sea Vents

At the edge of a mid-ocean ridge, warm mineral-rich water rises through cracks in the seafloor. Around those cracks, Riftia pachyptila grows in white tubes, with red plumes opening into the seawater. The species has no mouth or digestive tract. Its food comes from bacteria living inside a specialized organ called the trophosome. 1

This episode follows that arrangement slowly. It begins with the geology of a vent, then moves through the tube, the plume, the worm's unusual blood, and the bacteria that turn vent chemistry into energy. It also returns to the first sightings of lush vent communities at the Galápagos Rift in 1977, and to the patient work of submersibles and repeated sampling. 2

The central idea is simple, though the biology is not. A tube worm does not live on sunlight. It lives beside a chemical boundary, and carries that boundary inside its body.

The white tubes are built by the worm as it grows. The red plume acts as a respiratory surface, taking up oxygen from seawater and hydrogen sulfide from vent fluids. Special hemoglobin can carry both substances at once, which allows the worm to supply its internal bacteria without bringing the most dangerous chemicals directly into ordinary animal tissues. 1

The 1977 Galápagos Rift expedition revealed communities that had never been seen by people before. Later expeditions used the submersible Alvin to photograph, map, sample, and revisit vent fields whose animal communities could change after volcanic eruptions. 2