Figure 6

Presence or absence of tubules in other gastropod species. A. Shell of the false abalone Stomatella impertusa. B. Shell of the limpet Diodora sp. C. Toluidine blue stained cross-section of the mantle of the false abalone in A. The location of the shell is indicated by a dotted line. Scale bar = 100 μm. D. TEM of boxed area in C. Several tubule-like invaginations are visible. These are filled with microvilli (mv), and open to the dorsal surface (*). Scale bar = 20 μm. E. Higher magnification of D. The cells lining the invagination are not as columnar as those lining abalone tubules (compare to Figure 2B and C), and do not appear to contain electron-lucent vesicles. Despite this, secretions can be observed within the lumen (black arrowhead). Scale bar = 10 μm. F. Toluidine blue stained cross-section of the mantle of the keyhole limpet in B. The location of the shell is indicated by a dotted line. Scale bar = 100 μm. G. TEM of boxed area in F. Some folding of the epithelium is apparent, but these are no deeper than one cell layer. The epithelium is covered with microvilli (mv), and secretions are visible (black arrowhead). Scale bar = 2 μm.