Diploria
Monotypic genus of massive reef-building stony corals.
Diploria is a genus of stony corals that build massive reefs, belonging to the family Mussidae. It contains just one species: *Diploria labyrinthiformis*, better known as grooved brain coral. This coral lives in the western Atlantic Ocean and the Caribbean Sea, and its surface has a maze-like pattern.
The coral grows in a hemispherical, brain-shaped form and can be brown, yellow, or grey. Its surface is marked by deep, connected double-valleys, each separated by grooved ridges called ambulacra. The valleys and grooves may differ in color. *Diploria labyrinthiformis* grows upward at about 3.5 millimeters per year and can reach roughly 2 meters (6.6 feet) across. During its planktonic larval stage, it can move, but afterward it becomes permanently attached to the seafloor.
This species feeds by suspension, mainly on zooplankton and bacteria. Its polyps capture prey by extending mesenterial filaments and tentacles, using nematocysts to immobilize it. Mucus and cilia then move the prey to the mouth. The coral is hermaphroditic and reproduces through broadcast spawning, releasing eggs and sperm into the water for external fertilization. Unlike most other Caribbean broadcast spawners, it spawns over several months, from late spring to mid-autumn.
*Diploria labyrinthiformis* is found in tropical parts of the western Atlantic Ocean, the Gulf of Mexico, the Caribbean Sea, the southern tip of Florida, the Bahamas, Bermuda, and the coasts of Central America. It lives offshore at depths from 1 to 30 meters (3.3 to 98.4 feet). The coral is important to scientists because the layers in its skeleton can reveal past changes in ocean temperature.
For years, the IUCN Red List listed this species as Least Concern, but the 2021 assessment uplisted it due to a predicted decline, partly because it is vulnerable to stony coral tissue loss disease.
The coral hosts *Zooxanthella*, a symbiotic dinoflagellate alga. The alga gains a protected, elevated home, while the coral receives nutrients from the alga’s photosynthesis, which supports its growth and calcification. It also benefits from the long-spined urchin *Diadema antillarum*, whose grazing reduces shading and prevents macroalgae overgrowth.
Despite having nematocysts, *Diploria labyrinthiformis* is preyed upon by gastropods, polychaetes, sea urchins, starfishes, sea spiders, and parrotfish and other fishes.
Quick Facts
- Taxon
- Diploria labyrinthiformis
Facts from the source article.
Lore & Background
Diploria labyrinthiformis has a hemispherical, brain-like shape with a brown, yellow, or grey colour. It has characteristic deep, interconnected double-valleys separated by grooved ambulacral ridges, with possible colour differences between valleys and grooves. The coral grows upward at about 3.5 millimeters per year and can reach about 2 metres in diameter. During its planktonic larval stage, it has locomotion; after that, it becomes permanently sessile.
This species is a suspension feeder, surviving mainly on zooplankton and bacteria captured by polyps using extruded mesenterial filaments and tentacles. Polyps have nematocysts that hold prey immobile, and prey is transported to the mouth with mucus and cilia. Diploria labyrinthiformis is hermaphroditic and reproduces through broadcast spawning, releasing eggs and sperm that fertilize at the water surface. Unlike most other Caribbean broadcast spawners, it spawns over multiple months from late spring until mid-autumn.
The coral hosts Zooxanthella, a symbiotic dinoflagellate alga, and has a relationship with Diadema antillarum, the long-spined urchin, whose grazing reduces shading and macroalgae overgrowth. Various predators include gastropods, polychaetes, sea urchins, starfishes, sea spiders, parrotfish, and other fishes. It is host to the parasite Corallovexia brevibrachium, which is both an ectoparasite and endoparasite.
Reader's Guide
Diploria labyrinthiformis is notable as the sole species in the genus Diploria, making it a monotypic taxon within the family Mussidae. Its maze-like appearance and hemispherical shape make it a recognizable reef-building coral in the western Atlantic and Caribbean. The species is ecologically significant as a host for symbiotic Zooxanthella algae, which provide nutrients for growth and calcification, and it interacts with the long-spined urchin Diadema antillarum to control macroalgae. Its growth layers help researchers study historical ocean temperature changes. The species was listed as Least Concern for years on the IUCN Red List, but a 2021 assessment resulted in a sudden uplisting due to predicted decline, partly from susceptibility to stony coral tissue loss disease. Its reproductive strategy—broadcast spawning over multiple months from late spring to mid-autumn—differs from many other Caribbean broadcast spawners. The coral also appears on postage stamps from Belize, the United States, and Mayotte.
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