Coral polyps are night eaters so, at night, the coral polyps will come out of their skeletons to feed. They will do this by extending their tentacles that also sting in order to capture prey. Nematocytes which are the stinging cells, incapacitate prey and scare predators. The tentacles are able to pull the prey into the polyp's mouth that is then digested by the stomach. The stomach cavity is divided by mesenteries, longitudinal membranes, that are able to increase stomach cavity surface area. Mesenteries aid in digestion and have digestive filaments that also help in capture food. 

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Stomach

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Coral polyps have stomachs that open at one end aka the mouth which has tentacles. Even after when food is consumed and ready to be excreted, the food waste products will exit through the same opening. This is considered an incomplete digestive system, the stomach being both a  mouth and anus. Within the entire polyp body, the stomach is also the largest portion of the body. The gastrovascular cavity absorbs nutrients and carries out extracellular digestion where enzymes break ingested food down. 

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Gastrodermis

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All cnidarians have symmetric body types. There are two tissue layers which are the epidermis (outside layer) and the gastrodermis (inner layer). The gastrodermis is important to the digestive system since it has glandular and phagocytic cells responsible for digestion and incorporation of nutrients Additionally, the gastrodermis has been a location where early signs of heat stress are expressed. 

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Digestive Filament

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Digestive filament are specialized ciliated, skinny structures. One lobe has cnidae (secretory products), mucocytes (synthesize and secrete mucus to help in feeding), collar cells (specialized ell in epithelia), and granular cells (secretory epithelial cells released into the gastrovascular cavity for extracellular digestion of prey) and extends from the coral polyp's mouth when feeding. 

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Coral Feeding

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Corals participate in a mutualistic symbiosis relationship which means both species benefits from each other. Corals have this relationship with dinoflagellates, single-celled eukaryotes like algae or marine plankton. Zooxanthella, a type of dinoflagellate, is responsible for most of the corals' carbon energy gain. In addition, corals are very dependent on elements like nitrogen, phosphorus, and sulfur. 

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