The first organisms to populate the vents are bacteria, then other microorganisms, including amphipods and copepods appear. Sometime later acorn worms, dandelion-like animals, and other species of shrimp and tube worms add to the expanding community. In their most advanced stages vents are home to mussels, a variety of worms, anemones, and a large population of crabs, as well as many of the earlier colonists. Some vent animals, like limpets, clams, and mussels feed directly on bacteria. Other animals, such as octopi, prey on those that eat bacteria.
Vent crabs act as both predator and scavenger.
Some of the most successful vent animals, tube worms and giant clams, form symbiotic relationships with chemosynthetic bacteria . The bacteria live within the animals' tissues and provide a built-in food supply. Tube worms have no mouth, gut, or anus. Nutrients are absorbed directly into tissues. Two species of tube worms inhabit hydrothermal vent s.