Fig. 10. High-resolution NanoSIMS image of a 2 µm-thick, freeze-substituted section of Galaxea fascicularis after 1 min incubation in ⁴⁴Ca artificial seawater in the light. The ⁴⁴Ca/⁴⁰Ca ratio image (A) and line profile (B) indicate that ⁴⁴Ca had reached a high relative concentration in the unspecialised oral ectodermal cells but little exchange had occurred in the mucocytes (Mu) or cnidocytes (Cn). Natural (unenriched) levels are also indicated. SW, external seawater layer. In B the ratio ⁴⁴Ca/⁴⁰Ca along B–A in (A) is plotted against distance (µm).