Pillar coral (''Dendrogyra cylindrus'') is a hard coral (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 ...
) found in the western Atlantic Ocean and the
Caribbean Sea
The Caribbean Sea ( es, Mar Caribe; french: Mer des Caraïbes; ht, Lanmè Karayib; jam, Kiaribiyan Sii; nl, Caraïbische Zee; pap, Laman Karibe) is a sea of the Atlantic Ocean in the tropics of the Western Hemisphere. It is bounded by Mexico ...
. It is the only species in the monotypic genus ''Dendrogyra''. It is a digitate coral -that is, it resembles fingers (Latin ''digites'') or a cluster of cigars, growing up from the
sea floor without any secondary branching. It is large and can grow on both flat and sloping surfaces at depths down to 20 m (65 ft). It is one of the few types of hard coral in which the
polyps can commonly be seen feeding during the day.
Description
Pillar coral forms an encrusted base from which grow vertical cylindrical, round-ended columns. This coral can grow to a height of with pillars more than wide but is usually much smaller than this. The
corallites from which the
polyps protrude are smaller than in diameter and arranged in shallow meandering valleys with low ridges in between. The skeleton of the coral is not usually visible because the polyps are typically extended during the daytime, unlike most other coral species.
[ The mass of undulating tentacles gives the coral a furry appearance. This coral is usually some shade of beige or brown.
]
Distribution and habitat
Pillar corals are found in the warmer parts of the western Atlantic Ocean and the Caribbean Sea. Within its range, ''D. cylindrus'' is common in some places, but rare in other seemingly suitable locations. Some of the islands in the Bahamas have plentiful numbers of colonies as does the north coast of Jamaica. It used to be common on the reefs off the coast of Florida
Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...
but has suffered from over-collection there. It seems to be absent from Bermuda and the coasts of Panama and Colombia. It usually grows on level or slightly sloping parts of the reef at depths between .
Biology
Pillar coral is a zooxanthellate
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 ''Sy ...
species, with symbiotic dinoflagellate algae living within the tissues. In sunlight these undergo photosynthesis
Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...
and most of the organic compounds they produce are transferred to their host, while they make use of the coral's nitrogenous wastes. These algae give the coral its brownish colour and restrict it to living in shallow water into which the sunlight can penetrate.[
Pillar coral is a slow-growing, long-lived species. A number of columns grow up from a basal plate; if the whole colony is dislodged and topples over, new cylindrical pillars can grow vertically from the fallen coral. Some specimens have been found where this has happened more than once, and the history of the colony can be deduced from its shape. If a pillar gets detached and becomes lodged in a suitable position, it can continue to live, sending up new pillars from the base and other parts of the column.][
Each pillar coral clonal colony is either male or female. Sexual reproduction takes place with ]gamete
A gamete (; , ultimately ) is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. In species that produce ...
s being released into the water column
A water column is a conceptual column of water from the surface of a sea, river or lake to the bottom sediment.Munson, B.H., Axler, R., Hagley C., Host G., Merrick G., Richards C. (2004).Glossary. ''Water on the Web''. University of Minnesota-D ...
where fertilisation takes place. The larva
A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle.
...
e that develop from the eggs
Humans and human ancestors have scavenged and eaten animal eggs for millions of years. Humans in Southeast Asia had domesticated chickens and harvested their eggs for food by 1,500 BCE. The most widely consumed eggs are those of fowl, especial ...
are plankton
Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucia ...
ic and drift with the currents before settling on the seabed to found new colonies.[
]
Status
The IUCN Red List of Threatened Species lists pillar coral as being " Critically Endangered". This is because recruitment and survival rates of juveniles is low and this coral is particularly susceptible to both bleaching
Bleach is the generic name for any chemical product that is used industrially or domestically to remove color (whitening) from a fabric or fiber or to clean or to remove stains in a process called bleaching. It often refers specifically, to ...
and white plague disease. It is resistant to strong wave action but can be wrecked by hurricane
A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depend ...
s and tropical storms. However, broken fragments regenerate well. Some of the localities in which it is found are in marine parks and in these it should be safe from human disturbance. In addition, the advent of stony coral tissue loss disease in Florida and the Caribbean is causing local extinctions and may have species-level effects on this species as it is infected at an early stage of the disease progression.
Gallery
Image:Pillar1_Marker32_2010.jpg, A large colony at Marker 32 reef in the Florida Keys, June 2010
Image:Pillar2_Marker32_2010.jpg, A small colony at Marker 32 reef in the Florida Keys, June 2010
Image:Dendrogyra cylindrus.jpg, A large colony
Image:Dendrogyra cylindrus01.jpg, A skeletal specimen from Fort Napoléon, Guadeloupe, December 2006
References
*
External links
NOAA Fisheries Species Directory - Pillar Coral
Brief video of small specimen in Florida Keys
{{Taxonbar, from=Q28182
Meandrinidae
Corals described in 1834
ESA threatened species
Taxa named by Christian Gottfried Ehrenberg