The worm has a red plume that emerges from a protective tube. It has a head, collar, trunk and anchor, but no mouth, eyes, or gut. Scientists once called these tube worms "gutless wonders." They could not understand how an animal without a mouth or gut could survive.

In time, scientists discovered that the tube worms survive by chemosynthesis in a symbiotic relationship with the billions of bacteria that are packed inside each of them. The worm provides a home for the bacteria. In 29 g (1 oz.) of tissue inside the tube worm, there are 285 billion bacteria! The worm's red plume contains hemoglobin. This hemoglobin, unlike human's, can bind oxygen and hydrogen sulfide in the water separately (to keep the hydrogen sulfide from poisoning the worm) before carrying both to the bacteria. The bacteria oxidize the hydrogen sulfide and convert carbon dioxide into nourishment for the worm. Solid sulfur remains embedded in the organism as waste. Giant clams have a similar symbiotic relationship with bacteria.

How did the bacteria enter the worm? Researchers discovered that, in their earliest stages, tube worms have a mouth and gut for bacteria to enter. Later the mouth disappears and the gut closes.

Eyeless Shrimp!

Certain vents, particularly in the Mid-Atlantic Ridge, teem with tiny shrimp. Biologists have counted 1500 shrimp in just .8 square meter (1 sq. yd.) at an Atlantic vent. These are not shrimp you'd want on your plate; hydrogen sulfide makes them reek of rotten eggs. The shrimp use their claws to scrape sulfides from chimneys and stuff them into their mouths. At first researchers considered the shrimp eyeless, a not-so-surprising feature considering the inky darkness of the ocean floor.

Shrimp dominate the Atlantic vents

Later research revealed, however, that at least some shrimp have detectors for an hitherto unknown phenomenon--vent glow. This glow is one of the unsolved mysteries of vents. The shrimp also appear able to detect hydrogen sulfide, which may provide clues to colonization of vent communities--another unsolved vent mystery.

Pompeii worms? -->
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