Alkaline phosphatase (AP) and peroxidase (PO) activity in the evaginating shell gland and expanding shell field of L. stagnalis . All panels are double labelled for AP and PO activity. A-A”’ (77 hpfc). By 77 hpfc secreted birefringent material (black arrow in A) overlying the evaginating shell gland is clearly visible. The shell gland is no longer a closed lumen (cf. Figure 4A and 4B) as it continues to evaginate (indicated by transparent white arrows in A). A ring of intense PO activity now surrounds a field of AP activity (A’). The protonephridia (pn) remain intensely AP+ (A”). B-B”’ (87 hpfc). By 87 hpfc shell gland evagination appears to be complete and the field of AP+ cells in the shell gland has expanded in all directions (B’). A sheet of organic material overlies the shell field (arrow in B”’). C-C”’ (97 hpfc). At 97 hpfc the shell field continues to increase in size and the border between PO+ and PO- cells at the shell field margin sharpens (C”’). D-D”’ (117 hpfc). By 117 hpfc AP activity in the shell gland is concentrated in cells directly adjacent to PO+ cells. All larvae are oriented with the shell field to the left. An asterisk marks the position of the stomodaeum. Scale bars are 20 μm (A”’, B”’, C”’ and D”’) or 50 μm (A-A”, B-B”, C-C” and D-D”). Numbers in the lower left of each panel row indicate the age in hours post first cleavage (hpfc). Panel A'' is 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