Hermatypic corals are those

coral Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and ...

s in the order

Scleractinia Scleractinia, also called stony corals or hard corals, are marine animals in the phylum Cnidaria that build themselves a hard skeleton. The individual animals are known as polyps and have a cylindrical body crowned by an oral disc in which a ...

which build reefs by depositing hard calcareous material for their skeletons, forming the stony framework of the reef. Corals that do not contribute to

coral reef A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups. C ...

development are referred to as ahermatypic (non-reef-building) species. Many reef-forming corals contain symbiotic photosynthetic

zooxanthella Zooxanthellae is a colloquial term for single-celled dinoflagellates that are able to live in symbiosis with diverse marine invertebrates including demosponges, corals, jellyfish, and nudibranchs. Most known zooxanthellae are in the genus '' Sym ...

e, which contribute to their nutritional needs. The term "hermatypic" is sometimes misused, being assumed to apply to all zooxanthellate corals. However, there are zooxanthellae in many non reef-forming corals; and not all hermatypic corals in shallow water contain zooxanthellae. Further, some hermatypic corals live at depths to which light cannot penetrate; they form deep-water reefs but do not harbour the symbionts.

References

Coral reefs Anthozoa Scleractinia {{coral-stub