''Dichocoenia'' is a monotypic

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

stony coral 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 ...

in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Meandrinidae The Meandrinidae are a family of stony corals. The name comes from the Greek, ''maiandros'' meaning "meandering", referring to the miniature, winding valleys found between the corallites. Fossil corals in this family have been found dating back ...

. It is represented by a single species, ''Dichocoenia stokesii'', which is commonly known as pineapple coral, elliptical star coral, or pancake star coral. It is found in the Caribbean Sea and the western Atlantic Ocean. ''Dichocoenia stokesii'' has irregular calyces and its form can be either a massive, hemispherical hump or a flat, platform-like structure.

Description

''Dichocoenia stokesi'' is a massive

colonial Colonial or The Colonial may refer to: * Colonial, of, relating to, or characteristic of a colony or colony (biology) Architecture * American colonial architecture * French Colonial * Spanish Colonial architecture Automobiles * Colonial (1920 au ...

coral that forms rounded humps up to in diameter or thick plates. It is recognisable by the fact that many of the

corallite A corallite is the skeletal cup, formed by an individual stony coral polyp, in which the polyp sits and into which it can retract. The cup is composed of aragonite, a crystalline form of calcium carbonate, and is secreted by the polyp. Corallit ...

s, the stony cups from which the coral polyps protrude, can be oval, or elongated. They can be up to long and only wide. Others are circular or Y-shaped and all have raised rims. The columella, the central axial structure in the corallite, is fragile and spongy. The polyps are large and well-separated with a diameter of about . The colour is variable and can be white, cream, orange, yellowish-brown, green, olive or brown and the septo-costae, the little ridges that surround the corallites, are white. Sometimes two individual corals grow side by side and intertwine, forming one hump, but in these circumstances they do not fuse and each retains its original colour.

Distribution and habitat

''Dichocoenia stokesi'' is found in the western Atlantic Ocean and Caribbean Sea. Its range extends from

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and southern

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 ...

to the southern half of the

Gulf of Mexico The Gulf of Mexico ( es, Golfo de México) is an oceanic basin, ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of ...

and along the coast of Central America to Venezuela. The

fossil record A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in ...

shows that this species grew in the Caribbean region as long ago as the

Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...

Era (34 to 23 million years ago). It is a relatively uncommon species and tends to grow on fore reefs and back reefs but not on reef crests. It has a wide depth range of 2 to 72 metres (6 to 236 feet) but is commonest at or less. The corallites are larger and more prominent in individuals growing at greater depths.

Biology

''Dichocoenia stokesi'' 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 ...

coral. Single celled

symbiotic Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasit ...

green algae live within the tissues. These use the coral's nitrogenous waste and supply the coral with the organic products of

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 ...

. During the day, the coral's polyps are retracted but at night they emerge and the

tentacle In zoology, a tentacle is a flexible, mobile, and elongated organ present in some species of animals, most of them invertebrates. In animal anatomy, tentacles usually occur in one or more pairs. Anatomically, the tentacles of animals work main ...

s are extended to catch plankton and small invertebrates. This coral is not much affected by

predation Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill the ...

but is eaten by some

bivalve molluscs Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bival ...

and is sometimes overgrown by

sponge Sponges, the members of the phylum Porifera (; meaning 'pore bearer'), are a basal animal clade as a sister of the diploblasts. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate through t ...

s. The sexes are separate in ''Dichocoenia stokesi''. There seem to be two mass spawning events during the year, one at the end of August and the other in October. The free-swimming

planula A planula is the free-swimming, flattened, ciliated, bilaterally symmetric larval form of various cnidarian species and also in some species of Ctenophores. Some groups of Nemerteans also produce larvae that are very similar to the planula, which ...

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. The ...

e eventually settle on the seabed and develop into juvenile polyps which found new colonies.

Status

Although ''Dichocoenia stokesi'' is susceptible to

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 ...

, it is considerably more tolerant of thermal stress than many other stony coral species. It is very susceptible to the disease white plague, especially at high water temperatures. In the

Florida Keys The Florida Keys are a coral cay archipelago located off the southern coast of Florida, forming the southernmost part of the continental United States. They begin at the southeastern coast of the Florida peninsula, about south of Miami, and e ...

in 1995 there was an

epizootic In epizoology, an epizootic (from Greek: ''epi-'' upon + ''zoon'' animal) is a disease event in a nonhuman animal population analogous to an epidemic in humans. An epizootic may be restricted to a specific locale (an "outbreak"), general (an "epi ...

of white plague type II and 75% of ''Dichocoenia stokesi'' colonies were killed. Because of its slow growth rate and low level of recruitment, recovery after this outbreak did not occur and the reef population seems to be permanently diminished. ''Dichocoenia stokesi'' is also susceptible to

black band disease Black band disease is a coral disease in which corals develop a black band. It is characterized by complete tissue degradation due to a pathogenic microbial consortium. The mat is present between apparently healthy coral tissue and freshly expo ...

ciliate infection The ciliates are a group of alveolates characterized by the presence of hair-like organelles called cilia, which are identical in structure to flagellum, eukaryotic flagella, but are in general shorter and present in much larger numbers, with a ...

and dark-spot syndrome.

References

{{Taxonbar, from1=Q3318999, from2=Q3330640, from3=Q3333121 Scleractinia genera Meandrinidae Corals described in 1848 Taxa named by Henri Milne-Edwards Taxa named by Jules Haime Monotypic cnidarian genera