Fig. 7

Maja brachydactyla. Secretory activity of the midgut caeca. Anterior midgut caeca, zoea II 6 days post-hatching, cell apex and lumen, TEM (A). Anterior midgut caeca, megalopa 10 days post-hatching, fusion between vesicles and apical cell membrane, TEM (B). Anterior midgut caeca, zoea II 6 days post-hatching, microvillus distended, TEM (C). Anterior midgut caeca, adult, epithelial fold and brush border surface, SEM (D). Posterior midgut caecum, adult, epithelial folds and brush border surface, SEM (E). Posterior midgut caecum, adult, detailed view of macro-apocrine secretion (secretory vesicles), SEM (F). Anterior midgut caeca, adult, detailed view of macro-apocrine secretion including cell apex and lumen, TEM (G). Anterior midgut caeca, adult, microvillus distended, TEM (H–I). Posterior midgut caecum, adult, microapocrine secretion (detailed view of the tiny secretion vesicles of the microvilli), SEM (J). Scale bars (nm): 500 (B–C, J); (μm): 1 (A, H–I), 2 (G), 5 (F), 20 (D–E). Abbreviations: arrowhead, vesicle-like distension of the microvillus; asterisk, cell-to-cell junction; EV, electron-dense vesicles (cytoplasm); FV, potential fusion between vesicle and apical cell membrane; HV, holes left after the release of the vesicles; LV, lucent vesicles (cytoplasm); Mv, microvilli; SV, secretory vesicles; VL, vesicle of the lumen