Colpophyllia natans
Encyclopedia
Colpophyllia natans, known as boulder brain coral and large-grooved brain coral, is a species of stony coral
Scleractinia
Scleractinia, also called stony corals, are exclusively marine animals; they are very similar to sea anemones but generate a hard skeleton. They first appeared in the Middle Triassic and replaced tabulate and rugose corals that went extinct at the end of the Permian...

 found primarily in the Caribbean Sea and the Gulf of Mexico. It inhabits the slopes and tops of reefs, to a maximum depth of fifty metres. It is characterised by large, domed colonies, which may be up to two metres across, and by the meandering network of ridges and valleys on its surface. The ridges are usually brown with a single groove, and the valleys may be tan, green, or white and are uniform in width, typically 2 centimetres. The polyps only extend their tentacles at night.

Description

Individual colonies of Colpophyllia natans are large and usually broadly domed, with curvature typically increasing with the size, and therefore age, of the colony. They grow up to two metres in diameter and morphologically earn the epithet "boulder". Colony shape may occasionally be flat-topped discs, particularly when younger. As a type of brain coral
Brain coral
Brain coral is a common name given to corals in the family Faviidae so called due to their generally spheroid shape and grooved surface which resembles a brain...

, the surface of the skeleton is a network of winding, curving valleys and ridges (or walls) that roughly resemble the familiar folding architecture of the mammal cerebrum.

The colour of the ridges and valleys vary among colonies, with the ridges being various shades of brown, and the valleys either whitish, green, or tan. The ridge tops are indented with a single thin groove. Ridges and valleys may be up to 2 centimetres wide, and this breadth distinguishes it from the narrower Diploria, which may otherwise be similar in appearance. The polyps only extend their tentacles at night.

The robust shape, size, and slow growth of the boulder brain coral allows it more easily to survive conditions to which smaller and more fragile corals, such as the plate-like lettuce coral (Agaricia agaricites), succumb. C. natans and the sympatric and similarly named boulder star coral (Montastraea annularis
Montastraea annularis
Montastraea annularis, commonly known as the boulder star coral, is a species of coral that lives in the western Atlantic Ocean and is the most thoroughly studied and most abundant species of reef-building coral in the Caribbean to date. It also has a comprehensive fossil record within the Caribbean...

) are less likely to be smothered by algal bloom
Algal bloom
An algal bloom is a rapid increase or accumulation in the population of algae in an aquatic system. Algal blooms may occur in freshwater as well as marine environments. Typically, only one or a small number of phytoplankton species are involved, and some blooms may be recognized by discoloration...

, and have also weathered reef-wrecking Hurricane Allen
Hurricane Allen
Hurricane Allen was the first and strongest hurricane of the 1980 Atlantic hurricane season. It was one of the strongest hurricanes in recorded history, one of the few hurricanes to reach Category 5 status on the Saffir-Simpson Hurricane Scale on three separate occasions, and spent more time...

 off the coast of Jamaica in 1980. Corals in the Caribbean are susceptible to bleaching
Coral bleaching
Coral bleaching is the loss of intracellular endosymbionts through either expulsion or loss of algal pigmentation.The corals that form the structure of the great reef ecosystems of tropical seas depend upon a symbiotic relationship with unicellular flagellate protozoa, called zooxanthellae, that...

 caused by high water temperatures and solar radiation. A nine-month study conducted in 2005 compared the mortality of C. natans from bleaching to that of Porites porites, which has a finger-like morphology. Although the severity of bleaching between the two species was similar, 56% of the P. porites colonies studied died from the bleaching, compared to only 8% mortality for bleach-affected C. natans. However, bleaching induced widespread incidence of the coral syndrome White Plague Type II, resulting in bleaching-related mortality of 42% among C. natans over 9 months, nearly as high as that for P. porites.

Distribution and habitat

Boulder brain corals inhabit coral reefs in the Caribbean Sea and the Gulf of Mexico, with most occurrences off the coasts of Belize
Belize
Belize is a constitutional monarchy and the northernmost country in Central America. Belize has a diverse society, comprising many cultures and languages. Even though Kriol and Spanish are spoken among the population, Belize is the only country in Central America where English is the official...

, eastern Yucatán Peninsula
Yucatán Peninsula
The Yucatán Peninsula, in southeastern Mexico, separates the Caribbean Sea from the Gulf of Mexico, with the northern coastline on the Yucatán Channel...

, southern Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...

, Puerto Rico
Puerto Rico
Puerto Rico , officially the Commonwealth of Puerto Rico , is an unincorporated territory of the United States, located in the northeastern Caribbean, east of the Dominican Republic and west of both the United States Virgin Islands and the British Virgin Islands.Puerto Rico comprises an...

, the Virgin Islands
Virgin Islands
The Virgin Islands are the western island group of the Leeward Islands, which are the northern part of the Lesser Antilles, which form the border between the Caribbean Sea and the Atlantic Ocean...

 and Cuba
Cuba
The Republic of Cuba is an island nation in the Caribbean. The nation of Cuba consists of the main island of Cuba, the Isla de la Juventud, and several archipelagos. Havana is the largest city in Cuba and the country's capital. Santiago de Cuba is the second largest city...

. It is identifiable in fossil records at least since the early Pliocene.

C. natans is considered one of the dominant reef-building corals of the Caribbean region and is a familiar species of the shallower reef ledges and slopes. It can be found down to a depth of fifty metres, but is more often established closer to the surface.

Lifecycle

Colpophyllia natans is a hermaphroditic broadcast spawner, releasing large numbers of gametes synchronously to aid fertilisation. Each individual polyp spawns both eggs and sperm, having the reproductive capabilities of both the male and female sexes. Following fertilisation, the zygote
Zygote
A zygote , or zygocyte, is the initial cell formed when two gamete cells are joined by means of sexual reproduction. In multicellular organisms, it is the earliest developmental stage of the embryo...

 becomes a microscopic larva called a planula
Planula
A planula is the free-swimming, flattened, ciliated, bilaterally symmetric larval form of various cnidarian species. The planula forms from the fertilized egg of a medusa, as the case in scyphozoans and some hydrozoans, or from a polyp, as in the case of anthozoans...

, which, upon swimming to suitable substrate, will anchor and establish a new colony. This method of sexual reproduction has a high rate of failure in several of its stages and few new colonies successfully grow.

C. natans is susceptible to more coral diseases than most other corals in its habitat. A total of seven diseases are known to afflict C. natans, and it is one of only twenty-two coral species worldwide in which this count is higher than three. It is one of the Caribbean corals most afflicted by black band disease
Black band disease
Black band disease is characterized by complete coral tissue degradation due to a pathogenic microbial consortium that appears as a dark red or black migrating microbial mat. The mat is present between apparently healthy coral tissue and freshly exposed coral skeleton.-Appearance:Black Band disease...

, and along with Montastraea spp., suffers from yellow-band disease
Yellow-band disease
Yellow-band disease is a disease that attacks colonies of coral at a time when coral is already under stress from pollution, overfishing, and climate change...

. A particularly aggressive form of white plague
Aurantimonadaceae
The Aurantimonadaceae are a small family of marine bacteria. There are three known species. Aurantimonas coralicida causes a white plague in corals, progressively destroying their tissues and leaving an expanding area that appears bleached. It has been epidemic in the Caribbean. The individual...

 known as WPL III has so far been documented attacking only very large colonies of C. natans and Montastraea annularis. Other hosted diseases include white plague types I and II, dark spot, and skeletal anomalies, such as tumours and galls. Another pathogen, so far unidentified, killed in one year, between 2001 and 2002, approximately half of the corals present in Bird Key Reef of the Dry Tortugas
Dry Tortugas
The Dry Tortugas are a small group of islands, located at the end of the Florida Keys, USA, about west of Key West, and west of the Marquesas Keys, the closest islands. Still further west is the Tortugas Bank, which is completely submerged. The first Europeans to discover the islands were the...

.

Despite this susceptibility to disease, the boulder brain coral is long-lived, with specimens capable of living for more than two hundred years.

Taxonomy

The first description of Colpophyllia natans as a species was published by the Dutch physician and naturalist Maarten Houttuyn
Martinus Houttuyn
Maarten Houttuyn or Houttuijn , Latinised as Martinus Houttuyn, was a Dutch naturalist.Houttuyn was born in Hoorn, studied medicine in Leiden and moved to Amsterdam in 1753. He published many books on natural history. His areas of interest encompassed Pteridophytes, Bryophytes and Spermatophytes...

. Basing his work on Linnaeus, between the years 1761 and 1785 Houttuyn published a 37-volume natural history series, titled ("Natural history, or an extensive description of the animals, plants and minerals, after the compilation of Linnaeus, with accurate illustrations"). Volumes 17 and 18, the final volumes of the zoology section, were published in 1772 and focused on polyps, wherein C. natans is described. Houttuyn gave the species name as Madrepora natans, which was later included in the genus Colpophyllia, by Henri Milne-Edwards
Henri Milne-Edwards
Henri Milne-Edwards was an eminent French zoologist.Henri Milne-Edwards was the 27th child of William Edwards, an English planter and militia colonel in Jamaica and Elisabeth Vaux, a French. He was born in Bruges, Belgium, where his parents had retired. At that time, Bruges was a part of the...

 and Jules Haime, 1848. His cousin Frans Houttuyn, a printer and bookseller, printed the series and is sometimes mistakenly credited for the work and also erroneously named as Houttuyn's father.

A synonym of C. natans is Meandrina gyrosa, attributed to Lamarck
Jean-Baptiste Lamarck
Jean-Baptiste Pierre Antoine de Monet, Chevalier de la Marck , often known simply as Lamarck, was a French naturalist...

, 1816. There is dispute over whether or not Colpophyllia breviserialis is the same species.
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