Barnacle Barnacle A barnacle is a type of arthropod constituting the infraclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosive settings. They are sessile (nonmotile) suspension feeders, and have two nektonic (active swimming) larval stages. Around 1,220 barnacle species are currently known. The name "Cirripedia" is Latin, meaning "curl-footed". The study of barnacles is called cirripedology. Barnacles are encrusters, attaching themselves permanently to a hard substrate. The most common, "acorn barnacles" (Sessilia), are sessile, growing their shells directly onto the
Ivory barnacle but that species is smaller, only growing to a height of . Another similar species is the striped barnacle ("Balanus amphitrite") but that has vertical pink lines on the test. The native range of the ivory barnacle extends from Nova Scotia to the Caribbean Sea and Gulf of Mexico but it has extended this range as a result of fouling the bottoms of ships and because its larvae are sometimes transported in ballast water. It was first seen in Pearl Harbor, Hawaii in 1929 and is now common in all the main islands. It is found, sometimes in great numbers,