Coral Polyp (IMAGE) Penn State Caption Reef corals comprise thousands or millions of genetically identical algal polyps, which remain attached to each other to produce massive colonies. This close-up shows Orbicella, an important reef-building coral in the Caribbean. The species and its symbiosis with micro-algae has been studied extensively Credit Robin T. Smith Usage Restrictions noncommercial use only License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.