Some observations on the Ca 2+-binding phospholipid from scleractinian coral skeletons

Abstract

1. 1. The lipid composition was determined of the skeletons and soft tissues of several reef-building corals. The phospholipids from these two sources were remarkable for binding Ca 2+-ions in vitro. 2. 2. The Ca 2+-binding capacity of skeletal phospholipid increased above pH 9.0, especially in the presence of CO 3 2− ions. The Ca 2+-binding capacity of the lipids was measured in the presence of various metals. The relative inhibition exerted by these metals was dependent on the kind of metal ions added to the reaction medium; in addition, there was a slight difference between lipids from the skeletons and the soft tissues. 3. 3. A histochemical test revealed the existence of sudanophilic material in skeletal organic matrix of a branching coral, Acropora hebes. 4. 4. These data suggest that the Ca 2+-binding phospholipids of the skeletons might serve as seeding sites for CaCO 3 depositions in the process of skeleton formation in scleractinians.