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.

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Submitted by Stephen Price (not verified) on

The polyp tentacles are not single simple ring around the oral disk - in this coral which looks like Porites porites. Tentacles alternate positions of closer and further away in concentric rings. The implications this configuration are important in particle (or zooplankton) retention in feeding.