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 ), 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.
Hohagen and Jackson BMC Developmental Biology 2013 13:27 doi:10.1186/1471-213X-13-27