Figure 6

Multiple alkaline phosphatase (AP) domains reveal a differentiated and complex organisation of the shell gland. A second domain of AP activity present within the shell gland and shell field (not described by Timmermans [17]), is located outside of the PO domain and can not be clearly detected after prior detection of PO activity (see Figure 5 and Figure 6A cf. 6A'). A-A''' (72 hpfc). This second AP⁺ domain associated with non-invaginated cells of the shell gland margin can first be detected at 50 hpfc (see white arrow in Figure 3C), and is more pronounced at 72 hpfc (white arrows in A-A'''). This AP⁺ domain subsequently decreases in strength. B-B”’ (87 hpfc). At 87 hpfc the distinct domains of AP activity associated with the evaginating shell gland (black arrows) and the non-invaginated cells of the shell gland margin (white arrows) are still visible. C-C''' (97 hpfc). By 97 hpfc the domain of AP activity associated with non-invaginated cells of the shell gland marginis considerably weaker (white arrows). It's position relative to PO⁺ cells can be seen clearly in C (white arrow). The larvae in A-A”’ are oriented with the shell field to the top, the larvae in B-C”’ are oriented with the shell field to the left. An asterisk marks the position of the stomodaeum. Scale bars are 20 μm (A-A’, B- B’ and C-C’) or 100 μm (A”-A”’, B”-B”’ and C”-C”’). Numbers in the lower left of each panel row indicate the age in hours post first cleavage (hpfc). Panels A”, A”’, B”, C and C”’ are reflected about the vertical axis for consistency of presentation.