Fig. 2. General organization and morphology of peptidergic endocrine cells in the Cancer anterior and posterior midgut caeca epithelia. Regardless of species (Cancer productus shown), immunolabel (anti-substance P in A and anti-SIFamide in B and C) or location within the midgut caeca (posterior midgut caecum in A and anterior midgut caecum in B and C), the gross organization and morphology of the intrinsic peptidergic endocrine cells was similar. Specifically, all cells possessed an enlarged basal region and extended a thin, beaded projection apically toward the midgut lumen. This organization is shown in longitudinal-section in A and in cross-section in B. The morphology of one peptidergic cell from B (arrow) is shown at higher magnification in C. (A) A single optical section. (B) A brightest pixel projection of 42 optical sections collected at 1.05-µm intervals. (C) A brightest pixel projection of 22 optical sections collected at 0.75-µm intervals. Scale bars, 200 µm (A,B) and 25 µm (C).