Acorn Barnacle (Balanus spp.)

acorn barnacles

The adult acorn barnacle (Balanus spp.) often lives in dense colonies attached to rocks, pilings, and other hard surfaces.
(Photo courtesy of Nancy Sefton)

The acorn barnacle is common in South Carolina estuaries (where rivers meet the sea). As an adult, this crustacean often lives in dense colonies attached to rocks, pilings, and other hard surfaces. The acorn barnacle gets its name from the acorn shape that is formed by the hard calcerous (containing calcium) plates protecting its soft body. Like all barnacles, the acorn barnacle feeds on microscopic plants and animals, which it filters out of the water. Acorn barnacles are eaten by snails, birds, fish, and crabs.