Desmocytes in the calicoblastic epithelium of the stony coral Mycetophyllia reesi and their attachment to the skeleton.

Desmocytes scattered over the surface of the corallum of the scleractinian Mycetophyllia reesi attach the calicoblastic tissue to the skeleton. The structure of the desmocyte is generally consistent with that of other scleractinians except for their more rectangular profiles and greater size. However, the extent of attachment is distinctive, and the mode of attachment to mineral is described for the first time. The skeleton contains dual rows of interconnected pits between the septa, within and among which desmocytes form virtually uninterrupted sheets. Desmocytes terminate with hemidesmosomes that attach the epithelium to a fibrillar basal lamina. Fibrils extend from the basal lamina into the skeletal matrix anchoring tissue firmly to the skeleton. In addition, the basal lamina itself appears to be incorporated within the organic matrix during growth, partitioning the skeleton into compartments. Because the skeletal organic matrix is physicochemically labile during demineralization, these intraskeletal details cannot be observed unless polycationic dyes such as Ruthenium red or other glycan precipitating agents are employed in the fixative sequence.