Barnacle

Barnacle Temporal range: Carboniferous–Recent PreꞒ Ꞓ O S D C P T J K Pg N
Chthamalus stellatus
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Thecostraca
Subclass:	Cirripedia Burmeister, 1834
Infraclasses
Acrothoracica (Gruvel, 1905) Rhizocephala (Müller, 1862) Thoracica (Darwin, 1854)
Synonyms
Thyrostraca Cirrhopoda Cirrhipoda Cirrhipedia

Barnacles are arthropods of the subclass Cirripedia in the subphylum Crustacea. They are related to crabs and lobsters, with similar nauplius larvae. Barnacles are exclusively marine invertebrates; many species live in shallow and tidal waters. Some 2,100 species have been described.

Barnacle adults are sessile; most are suspension feeders with hard calcareous shells, but the Rhizocephala are specialized parasites of other crustaceans, with reduced bodies. Barnacles have existed since at least the mid-Carboniferous, some 325 million years ago.

In folklore, barnacle geese were once held to emerge fully formed from goose barnacles. Both goose barnacles and the Chilean giant barnacle are fished and eaten. Barnacles are economically significant as biofouling on ships, where they cause hydrodynamic drag, reducing efficiency.