Calcification is an extremely widespread phenomenon occurring in organisms as diverse as bacteria, plants, sponges, clams and humans. Among the invertebrates, there are calcified structures that cover or encase their bodies such as coral reefs, snail shells, crab exoskeletons and sea urchin tests and spines. Other invertebrates form numerous usually microscopic calcified structures that impregnate the body called spicules or ossicles. The octocoral or sea whip Leptogorgia virgulata is an excellent example of an animal possessing elaborate spicules throughout its body. Like most invertebrate calcified structures, these spicules contain an internal organic matrix that provides a framework for the deposition of calcium carbonate. What is unusual, however, is our discovery that this octocoral spicule matrix contains collagen, a protein that is critical in the formation of bones and teeth, but is rarely associated with invertebrate calcium carbonate structure. Furthermore, this octocoral collagen varies seasonally, being predominant in the summer. This three-year project will explore in depth the relationships between octocoral spicule calcification over time will be studied using a variety of specific markers. For example, tetracycline is a fluorescent marker and 45Ca is a radioactive calcification. Radiolabelled proline and specific antibody markers that we have recently developed, mark collagen synthesis. These components can be visualized through fluorescence and transmission electron microscopy, and measured by quantifying the amount of label present. Bone remodelling involves changes in acidity and enzyme spicules using enzymatic reactions and other specific antibody markers. An important dimension of this project is the involvement of student investigators.
