Oulophyllia crispa
A near-threatened stony coral of the Indo-Pacific.
Oulophyllia crispa, also known as the intermediate valley coral, is a stony coral belonging to the family Merulinidae. It lives in the tropical western and central Indo-Pacific. Despite its broad distribution, the species is not common and its numbers appear to be dropping; the International Union for Conservation of Nature lists it as "near threatened."
This coral forms massive colonies shaped like hemispherical domes, stacks, or plates, which can reach over a meter across. In the Red Sea, however, colonies rarely exceed 20 centimeters. Its corallites are arranged in wide, winding valleys separated by sharp-edged ridges. The septa are thin, evenly spaced, and slope uniformly toward the central columella. The polyps are large and fleshy, emerging only at night, with white-tipped tentacles. The coral is typically brown, grey, or green, sometimes with contrasting oral discs. It resembles *Platygyra daedalea*.
The species ranges from the Red Sea, Gulf of Aden, and East Africa to Australia, Japan, the East China Sea, and various West Pacific island groups. It inhabits reefs down to about 30 meters deep, mostly on subtidal rocks and in lagoons.
*Oulophyllia crispa* is a zooxanthellate coral, hosting unicellular dinoflagellates in its transparent tissues. These algae use sunlight to produce organic carbon molecules for the coral. As the coral grows, its polyps do not fully divide, leaving several mouths within each large corallite. Boring sponges (*Cliona* spp.), polychaete worms, and bivalve mollusks drill into the colonies, causing bioerosion.
Quick Facts
- Taxon
- Oulophyllia crispa
Facts from the source article.
Lore & Background
Colonies of this coral form massive hemispherical domes, stacks or plates that can be a metre (yard) or more across, but in the Red Sea, it seldom exceeds 20 centimetres (8 in). The corallites are arranged in broad meandering valleys with acute-edged ridges separating them. The septa are thin and evenly spaced, and slope uniformly to the central columella. The polyps only expand at night; they are large and fleshy and have white-tipped tentacles. The colour of this coral is usually some shade of brown, grey or green, sometimes with contrasting oral discs. This coral is somewhat similar in appearance to Platygyra daedalea.
This coral is found in the tropical western and central Indo-Pacific region. Its range extends from the Red Sea, Gulf of Aden and East Africa to Australia, Japan, the East China Sea and the island groups of the West Pacific Ocean. It is found on reefs at depths down to about 30 metres (100 ft), mostly occurring on subtidal rocks and in lagoons.
Oulophyllia crispa is a zooxanthellate coral that has unicellular dinoflagellates embedded in its soft, transparent tissues. These use sunlight to create organic carbon molecules that the coral can use. As this coral grows, the polyps do not divide completely, resulting in several mouths being present in each large corallite. Boring sponges (Cliona spp.), polychaete worms and bivalve molluscs bore holes into colonies of this coral, causing bioerosion.
Reader's Guide
Oulophyllia crispa is notable for its wide but uncommon distribution across the tropical western and central Indo-Pacific, from the Red Sea and East Africa to Australia, Japan, and the West Pacific. Its near-threatened status, as rated by the IUCN, reflects a decreasing abundance despite its broad range. Ecologically, it is a zooxanthellate coral, relying on symbiotic dinoflagellates for energy through photosynthesis. Its growth form—massive hemispherical domes, stacks, or plates—can reach a meter across, though Red Sea colonies seldom exceed 20 centimeters. The coral's polyps are nocturnal, expanding only at night, and feature white-tipped tentacles. Bioerosion by boring sponges, polychaete worms, and bivalve molluscs affects colonies. The species is sometimes confused with Platygyra daedalea due to similar appearance. Its conservation concern highlights the vulnerability of even widespread coral species to environmental pressures.
Did You Know?
- Oulophyllia crispa is sometimes called the intermediate valley coral.
- Its polyps only expand at night and have white-tipped tentacles.
- In the Red Sea, colonies seldom exceed 20 centimetres (8 in), though elsewhere they can be a metre or more across.
More in Brain and Merulinid Corals 1-24
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