Fig. 6. Silver staining of live embryos of Hemigrapsus sexdentatus and H. crenulatus. Eggs were washed in distilled water, stained briefly with AgNO₃, washed again in distilled water and returned to seawater. (A–F) Appearance in vivo. In post-gastrula embryos a silver deposit is observed over the yolk (arrows). It is hypothesised that this patch corresponds to the embryonic dorsal organ and is responsible for water and salt excretion. Scale bars, 250 µm. (A) H. sexdentatus, stage 1, blastulae. Weak mottled silver staining over the whole embryo occasionally highlighting cell boundaries. (B) H. crenulatus, stage 2, gastrulae. (C) H. sexdentatus, stage 3, eyespots formed. (D) H. sexdentatus, stage 4–5, two yolk lobes. (E) H. crenulatus, stage 5, two yolk lobes, pre-hatching. (F) H. sexdentatus, Zoea. Some larvae hatched during staining. Free larvae did not stain but in those that hatched after staining, the silver deposit was cast off with the exuviae at the final embryonic moult (arrows). (G) Semi-thin epoxy section of AgNO₃ stained embryo of H. sexdentatus at stage 4 showing the dorsal surface and the yolk. A black deposit of silver is present between the outer and inner membranes. Scale bar, 25 µm.