Barnacles and Relatives: Thecostraca

All thecostracan larvae and some adult males of ascothoracids swim in open water. Adult barnacles are sessile and will usually attach themselves to rocks. They will also attach to other solid objects like shells, floating wood, wharf pilings, ship bottoms, and floating bottles or other trash. Most barnacles live at or just below the seashore, but some prefer living in deep-sea habitats near hot water geysers known as hydrothermal vents. Still others attach themselves to living animals, such as jellyfishes, crabs, other barnacles, sea turtles, sharks, and whales. The adults of parasitic species related to barnacles burrow into corals, the shells of mollusks, or live inside the bodies of other crustaceans. Most ascothoracids live on or inside the bodies of anemones, sea stars, and their relatives.