Dinoflagellate
Some dinoflagellates are zooxanthellae: endosymbionts of marine eukaryotes, and animals such as anthozoan corals. These reef-building corals largely depend on them. Other organisms which can host zooxanthellae include jellyfish, clams, foraminifera, sea slugs i.e. nudibranchs, and also ciliates and radiolaria.