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 st ructure of the desmocyte is generally consistent with that of other sclerac tinians except for their more rectangular profiles and greater size. Howeve r, the extent of attachment is distinctive, and the mode of attachment to m ineral is described for the first time. The skeleton contains dual rows of interconnected pits between the septa, within and among which desmocytes fo rm virtually uninterrupted sheets. Desmocytes terminate with hemidesmosomes that attach the epithelium to a fibrillar basal lamina. Fibrils extend fro m the basal lamina into the skeletal matrix anchoring tissue firmly to the skeleton. In addition, the basal lamina itself appears to be incorporated w ithin the organic matrix during growth, partitioning the skeleton into comp artments. Because the skeletal organic matrix is physicochemically labile d uring demineralization, these intraskeletal details cannot be observed unle ss polycationic dyes such as Ruthenium red or other glycan precipitating ag ents are employed in the fixative sequence. (C) 2001 Harcourt Publishers Lt d.