''Eusmilia'' is a genus of stony coral in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Meandrinidae. It is a

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unisp ...

genus represented by the

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

''Eusmilia fastigiata'', commonly known as the smooth flower coral. It is found on reefs in the

Caribbean Sea The Caribbean Sea is a sea of the Atlantic Ocean, North Atlantic Ocean in the tropics of the Western Hemisphere, located south of the Gulf of Mexico and southwest of the Sargasso Sea. It is bounded by the Greater Antilles to the north from Cuba ...

Description

Smooth flower coral is a colonial species that grows to about across. It forms a low mound of stony

calcium carbonate Calcium carbonate is a chemical compound with the chemical formula . It is a common substance found in Rock (geology), rocks as the minerals calcite and aragonite, most notably in chalk and limestone, eggshells, gastropod shells, shellfish skel ...

, the surface of which is covered with tubular projections, 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, in groups of one to three. The polyps protrude from these and are either round or oval, with the oval form being more common at moderate depths. They are large and widely spaced and are connected by a layer of translucent, jelly-like

mesoglea Mesoglea refers to the extracellular matrix found in cnidarians like coral or jellyfish as well as ctenophores that functions as a hydrostatic skeleton. It is related to but distinct from mesohyl, which generally refers to extracellular material f ...

tissue called

coenosarc In corals, the coenosarc is the living tissue overlying the stony skeletal material of the coral. It secretes the coenosteum, the layer of skeletal material lying between the corallites (the stony cups in which the polyp (zoology), polyps sit). The ...

which covers the surface of the carbonate skeleton. During the day they are retracted back into the cup-shaped corallites. These have large smooth-edged ridges called

septa SEPTA, the Southeastern Pennsylvania Transportation Authority, is a regional public transportation authority that operates bus, rapid transit, commuter rail, light rail, and electric trolleybus services for nearly four million people througho ...

, and the polyps have corresponding grooves at their base. At night, the polyps stretch out their translucent white tentacles to feed and the coral "flowers". This coral is usually cream, yellow or pale brown, often with a green or pink tinge.

Distribution and habitat

Smooth flower coral is found in the Caribbean, the Gulf of Mexico, the Bahamas and southern Florida, at depths down to about though it is commonest between . It is found on both the back and the front edges of reefs and is sometimes overhung by larger corals. It is listed as being critically endangered by the IUCN Red List of Threatened Species

Biology

The polyps remain retracted in the skeleton during the day but extend at night to feed. The tentacles search for

zooplankton Zooplankton are the heterotrophic component of the planktonic community (the " zoo-" prefix comes from ), having to consume other organisms to thrive. Plankton are aquatic organisms that are unable to swim effectively against currents. Consequent ...

and small invertebrates which are transferred to the mouth. Another major source of energy is the result of the

symbiotic Symbiosis (Ancient Greek : living with, companionship < : together; and ''bíōsis'': living) is any type of a close and long-term biolo ...

dinoflagellate The Dinoflagellates (), also called Dinophytes, are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered protists. Dinoflagellates are mostly marine plankton, but they are also commo ...

s which live within the coenenchyme and which produce nutrients by photosynthesis. The coral benefits from the carbohydrates produced and the algae use the coral's nitrogenous waste products.

Reproduction

Reproduction in corals takes place when gametes are released into the water. The fertilized

egg An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the ...

develops into a

planula A planula is the free-swimming, flattened, ciliated, bilaterally symmetric larval form of various cnidarian species and also in some species of Ctenophores, which are not related to cnidarians at all. Some groups of Nemerteans also produce larva ...

larva which forms part of the zooplankton and drifts with the current. After passing through a number of larval stages this settles on the sea bed and undergoes

metamorphosis Metamorphosis is a biological process by which an animal physically develops including birth transformation or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and different ...

into a polyp. The base of this secretes the

skeleton and the polyp founds a new colony, producing new polyps by budding.

References

{{Taxonbar, from1=Q13630238, from2=Q2785489 Scleractinia genera Monotypic cnidarian genera Meandrinidae