They have three developmental forms. All adults are attached to a substrate.
Barnacles are hermaphrodites .
Range and Habitat Barnacles are exclusively marine animals. They attach to rocks, shells, and other objects. Some barnacles are commensal on certain whales, turtles, fish, sponges, hydrozoans , and corals, among other animals. Barnacles bore into coral and old mollusks shells using chitinous teeth on the mantle as well as a chemical process to dissolve the shell. In 1830 the larval stages were first discovered, and the relationship between barnacles and crustaceans was established.