A Coral-Eating Barnacle

Abstract

Many rock barnacles form close associations with other organisms, yet none are known to have become wholly parasitic. In a study of balanids inhabiting corals, we encountered a species-Pyrgoma monticulariae Gray, 1831-that depends on the coral for both habitat and food. In achieving this relationship it has gained control over certain metabolic activities of the coral, including calcification, proliferation of coenenchyme, and nematocyst discharge. While balanids became associated with corals 25 million years ago, evidence suggests that this wholly parasitic relationship has developed within the last 10 million years.