Hemocyte-mediated shell mineralization in the eastern oyster

Abstract

The growth of molluscan shell crystals is usually thought to be initiated from solution by extracellular organic matrix. We report a class of granulocytic hemocytes that may be directly involved in shell crystal production for oysters. On the basis of scanning electron microscopy (SEM) and x-ray microanalysis, these granulocytes contain calcium carbonate crystals, and they increase in abundance relative to other hemocytes following experimentally induced shell regeneration. Hemocytes are observed at the mineralization front using vital fluorescent staining and SEM. Some cells are observed releasing crystals that are subsequently remodeled, thereby at least augmenting matrix-mediated crystal-forming processes in this system. Molluscan shell formation is often cited as resulting in large measure from extracellular events mediated by organic matrix secreted from the mantle epithelium (1–3). The ma-trix-mediated hypothesis states that the com