Giant tube worms (Riftia) from the Pacific can reach 3 meters (10 feet) in length. They are the fastest growing marine invertebrate known. They can grow 1 - 2 mm per day, or more than 33 inches (8.38 cm) a year. We'll capture a few with our submersible's mechanical arms and take them back in a special "critter-gitter" container for study.

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. 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.

Neat Fact: In 29 g (1 oz.) of tissue inside the tube worm, there are 285 billion 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. At first researchers considered the shrimp eyeless, a not-so-surprising feature considering the inky darkness of the ocean floor.

Neat Fact: 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.