Most calcareous structures of invertebrates contain an organic matrix that plays a primary role in calcification. The calcium carbonate spicules of the octocoral Leptogorgia virgulata form in association with an organic matrix. The protein of EDTA-insoluble matrix is predominantly collagenous in the summer, but contains little collagen in winter. The association of collagen in calcium carbonate skeletons and its seasonal variability are very unique in biomineralization systems. The reduction of collagen in winter suggests spicule decalcification and subsequent collagen degradation which can be seen under electron microscope examination. The research plan involves a comprehensive biochemical analyses of the organic matrix composition of the spicules at different times of the year. The study is coupled to electron microscope investigations of the spicules and matrices. These studies are important to elucidate the remodeling of the skeletal structures of biological systems. Additionally a immunocytochemical study at the ultrastructural level is planned to determine which component of the soluble and insoluble spicule matrices, i.e., collagen, glycoproteins etc., is responsible for nucleation of calcium carbonante crystals. The study will clarify a number of questions about the roles of matrices in initiation and inhibition of biological crystal growth, an area that has been historically disputed.
