Figure 2

Ultrastructure of the prismatic zone epithelium. A. Toluidine blue stained cross-section of the juvenile mantle. Epithelial invaginations can be found within the prismatic zone (black arrows). Scale bar = 50 μm, pg; periostracal groove. B. TEM of an invagination (tubule). The lumen of the tubule opens to the dorsal mantle surface (*) and is lined by cells containing numerous vesicles (white arrowheads). The surfaces of these cells are lined with microvilli (mv) that fill the lumen. Scale bar = 20 μm. C. TEM of a cross-section through a tubule. Vesicles are localised towards the apical (lumen-facing) surface of the cell (white arrowheads). A second cell type containing electron-dense vesicles can be observed (glandular cell; g). Scale bar = 5 μm, mv; microvilli. D. TEM of the apical cell surface lining the lumen. Electron lucent vesicles (white arrowhead) are similar in appearance to secretions that can be seen in the lumen (black arrowheads). Scale bar = 1 μm, mv; microvilli, mi; mitochondria. E. TEM of the apical cell surface lining the lumen. Adherens junctions (white arrows) can be observed between adjacent cells. Vesicles (white arrowheads) and secretions (black arrowhead) are also visible. Scale bar = 1 μm, mv; microvilli.