Abstract. – Most scleractinian corals and many other cnidarians host intracellular photosynthetic dinoflagellate symbionts. The symbionts contribute to host metabolism and skeletogenesis to such extent that this symbiosis is well recognized for its contribution in creating the coral reef ecosystem. However, the significance of this animal-microeukaryote association as the only widespread infection of animal cells by a mutualistic microeukaryote has yet to be explored. This is in stark contrast to the abundance of parasitic micro-eukaryotic infections of animals cells, including Plasmodium, Toxoplasma, Leishmania, and Entamoeba. Coral symbiologists can learn from the many analogous systems which are much better understood – that is, pathogenic infections of animal cells by microbes. The key areas to examine include the initial recognition event, invasion or uptake into a host cell, manipulation of the host cell response, replication within the host cell, and responses to the host’s immune response. Examples of these betterstudied systems offer new ideas and approaches for understanding and investigating the creation and composition of the intracellular niche in the cnidarian-dinoflagellate interaction.