What Is Coral? A Coral Polyp and Zooxanthellae

What are corals? Corals themselves are animals. But tropical reef-building corals have tiny plant-like organisms living in their tissue. The corals couldn’t survive without these microscopic algae–called zooxanthellae (zo-zan-THELL-ee). This cutaway diagram of a coral polyp shows where the photosynthetic algae, or zooxanthellae, live—inside the polyp’s tissue. The coral gives the algae a home. In return, the algae provide the coral with food. Learn more in the Ocean Portal's coral reef section and in this zooxanthellae slideshow.

What is coral? The answer is coral is an animal. This cutaway diagram of a coral polyp shows the location of its photosynthetic algae, or zooxanthellae, which coral needs to survive.

Smithsonian Institution