Symbiodinium

Zooxanthellae are protists that can live as endosymbionts in a number of organisms. The zooxanthellae are mostly to dinoflagellates, but also Chrysomonaden, cryptomonads and diatoms before coming. As hosts come foraminifera, stony corals ( Scleractinia ), many Octocorallia, other flowers animals ( Anthozoa ), fire coral ( Millepora ), giant clams ( Tridacnidae ) but also some jellyfish species. Also Nudibranch ( Nudibranchia ) (eg Pteraeolidia ianthina ) and sponges sometimes have zooxanthellae. All corals that are involved in the construction of tropical coral reefs, have zooxanthellae as endosymbionts.

The zooxanthellae live in the host's body and provide it with sugar, starch and other organic products. Both the host and the protists benefit from the symbiosis. The foraminifera symbiosis is optional, that is, both creatures thrive in principle also without each other. The reef-building corals of tropical coral reefs die, however, if they have expelled their zooxanthellae under stress, a phenomenon known as coral bleaching.

If not Protistenzellen as a whole, but only the chloroplasts are retained so one speaks of Kleptoplastie.