Fig. 1. Fluorescence emitted by algal-free coral nuclei (A–C), in hospite nuclei and cells (D–F) and coral-free algal nuclei and cells (G–I). A, D, G, DAPI (blue) for nuclei, chlorophyll auto fluorescent (red) for algal cells and 6-CFDA (6-carboxylfluorescein diacetate; green) for animal cells' cytoplasm. The holobiont state reveal coral cells with a single algal cell (D, no. 4), two algal cells in a single unit (D, numbers 1–3); three algal cells in a single unit (E) and sometimes more (C.R., unpublished). B, E, H ethidium bromide fluorescent intact nuclei; C, F, I comets, stained by ethidium bromide. DAPI was observed with Olympus filters U-MNU (excitation 360–370 nm); 6-CFDA labeling was observed with Olympus filter U-MW1B (excitation 460–490 nm). Scale bar (fitted all figures A–I, 10 µm).