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Fig.8: The zooxanthellate scleractinian coral Leptoseris fragilis lives under extreme low light conditions in depths between 90 and 145m. In the gastrodermis, the zooxanthellae (reddish dots) are found lying on a fluorescent screen formed by multilobed chromatophores which are densely packed with pigment granules filled with autofluorescent pigments. After excitation with short wavelengths the pigment of the host emit light of longer wavelengths are photosynthetically more useful for the zooxanthellae. Electron micrographs (TEM, SEM) are shown in Fig. 7.