Barnacles are crustaceans that are related to crabs, lobsters, and shrimps. They are sticky little creatures that attach themselves temporarily to a hard substrate or a symbiont such as a whale, a sea snake, or another crustacean, like a crab or a lobster. Barnacles feed on plankton in the water and, in turn, are eaten by a number of predators, including starfish, dogwinkles, and ribbon worms.
Barnacles can be found attached to piers, buoys, and boat hulls around the world. They secrete a fast-curing cement that is among the most powerful natural glues known, which is why they are difficult to remove from surfaces. Barnacles like places with lots of activity, like underwater volcanos and intertidal zones, where they reside on sturdy objects like rocks, pilings, and buoys.
Barnacles have a wide range of body plans, but one of the most bizarre is the rhizocephalan barnacle, which is an internal parasite in other crustaceans. They infiltrate and spread within the body of their host and even alter its behavior and appearance. Infected crabs can be detected by the external reproductive structure of the rhizocephalan that grows where the crab’s own eggs would be. The crab cleans and cares for this growth as if it were its own.
In summary, barnacles are crustaceans that attach themselves to hard surfaces and feed on plankton. They can be found in a variety of body plans, including as internal parasites in other crustaceans.
