''Alcyonium coralloides'', commonly known as false coral, is a colonial

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), ...

soft coral Alcyonacea is the old scientific order name for the informal group known as "soft corals". It is now an unaccepted name for class Octocorallia. It became deprecated . The following text should be considered a historical, outdated way of treatin ...

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 ...

Alcyoniidae Alcyoniidae is a family of leathery or soft corals in the phylum Cnidaria.Leathery cor ...

. It is native to the northeastern

Atlantic Ocean The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...

and the

Mediterranean Sea The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern Eur ...

. In the former location it generally grows as sheets or small lobes but in the latter it is parasitic and overgrows

sea fans Alcyonacea is the old scientific order name for the informal group known as "soft corals". It is now an unaccepted name for class Octocorallia. It became deprecated . The following text should be considered a historical, outdated way of treating ...

Taxonomy

This soft coral was first described in 1766 by the Russian naturalist

Peter Simon Pallas Peter Simon Pallas Fellow of the Royal Society, FRS FRSE (22 September 1741 – 8 September 1811) was a Prussia, Prussian zoologist, botanist, Ethnography, ethnographer, Exploration, explorer, Geography, geographer, Geology, geologist, Natura ...

who named it ''Parerythropodium coralloides''. It was later determined on the basis of its growth forms, the nature of its spicules (small skeletal elements) and the passages in its

coenenchyme Coenenchyme is the common tissue that surrounds and links the polyps in octocorals. It consists of mesoglea penetrated by tubes (''solenia'') and canals of the gastrodermis and contains sclerites, microscopic mineralised spicules of silica or of ...

(the tissue uniting the polyps) that it should be included in the genus ''

Alcyonium ''Alcyonium'' is a genus of soft corals in the family Alcyoniidae Alcyoniidae is a family of leathery or soft corals in the phylum Cnidaria.

'' and it was renamed ''Alcyonium coralloides''.

Distribution and habitat

''Alcyonium coralloides'' is plentiful in the Mediterranean Sea but less common on the Atlantic coast of Western Europe and in the

English Channel The English Channel, also known as the Channel, is an arm of the Atlantic Ocean that separates Southern England from northern France. It links to the southern part of the North Sea by the Strait of Dover at its northeastern end. It is the busi ...

. The northern limit of its range is Scotland. In the Atlantic Ocean, colonies are small and grow directly on vertical rock faces, under overhangs and in caves. In the Mediterranean, colonies usually grow on

such as '' Eunicella'', '' Paramuricea'' and '' Leptogorgia'', as well as on the

tunicate Tunicates are marine invertebrates belonging to the subphylum Tunicata ( ). This grouping is part of the Chordata, a phylum which includes all animals with dorsal nerve cords and notochords (including vertebrates). The subphylum was at one time ...

'' Microcosmus'' and on

coralline alga Coralline algae are red algae in the order Corallinales. They are characterized by a thallus that is hard because of calcareous deposits contained within the cell walls. The colors of these algae are most typically pink, or some other shade of re ...

e. Some species commonly colonised include ''

Eunicella singularis ''Eunicella singularis'', the white gorgonian, is a species of Colony (biology), colonial soft coral, a Gorgonian, sea fan in the family (biology), family Gorgoniidae. It is found in the western Mediterranean Sea, Adriatic Sea and Ionian Sea. It ...

'', '' Eunicella cavolinii'', ''

Eunicella verrucosa ''Eunicella verrucosa'', the broad sea fan, pink sea fan or warty gorgonian, is a species of colonial Gorgonian "soft coral" in the family Gorgoniidae. It is native to the north-eastern Atlantic Ocean and the western Mediterranean Sea. Descri ...

'', ''

Paramuricea clavata ''Paramuricea clavata'', the violescent sea-whip, is a species of Colony (biology), colonial soft coral in the Family (biology), family Plexauridae. It is found in shallow seas of the north-eastern Atlantic Ocean and the north-western Mediterrane ...

'' and '' Leptogorgia sarmentosa''.

Description

''Alcyonium coralloides'' has several different habits of growth. In the Atlantic Ocean it sometimes grows as encrusting sheets over rock surfaces. These are red with white or yellow polyps, sometimes having bare areas from which polyps are absent. More frequently, it grows in short finger-like lobes up to long, pale pink with white polyps. It seldom encrusts sea fans. In the Mediterranean, the habit of growth of ''Alcyonium coralloides'' is often encrusting, growing over the surface of a gorgonian. The sea fan has a rigid skeleton so ''Alcyonium coralloides'' does not need a supportive skeleton but it does however have spicules in its surface layers which makes it rough to the touch. The colour of the colony is often purple, but may be white, pink or yellow. The white and pink forms mainly occur in deep water and are considered mutants. The polyps, which are usually white, cream or yellow, may be long and are usually larger than those of the sea fan it is encrusting. It can be considered

parasitic Parasitism is a close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The ent ...

as the tissues of the sea fan are killed and ''Alcyonium coralloides'' adheres to the underlying skeleton. The mechanism by which it kills its host's tissues is not understood. Occasionally in the Mediterranean, this soft coral exhibits a lobed form similar to Atlantic colonies.

Biology

Like other soft corals, ''Alcyonium coralloides'' is a

suspension feeder Filter feeders are aquatic animals that acquire nutrients by feeding on organic matters, food particles or smaller organisms (bacteria, microalgae and zooplanktons) suspended in water, typically by having the water pass over or through a spec ...

. The polyps spread their pinnate tentacles wide and passively gather zooplankton and organic particles from the water flowing past. By colonising gorgonians, ''Alcyonium coralloides'' is raised above the surface of the

substrate Substrate may refer to: Physical layers *Substrate (biology), the natural environment in which an organism lives, or the surface or medium on which an organism grows or is attached ** Substrate (aquatic environment), the earthy material that exi ...

. This is advantageous to it as the water flow, and thus the supply of plankton, is enhanced. Colonies are either male or female and sexual reproduction occurs in Mediterranean populations. With a period of five or six months, the length of

gametogenesis Gametogenesis is a biological process by which diploid or haploid precursor cells undergo cell division and differentiation to form mature haploid gametes. Depending on the biological life cycle of the organism, gametogenesis occurs by meiotic d ...

is shorter than for any other littoral octocorals. Larvae have been observed in the gastric cavity of females in May and in the open water in June, being ready to settle in early summer, a time at which the host corals are most vulnerable because of their own breeding activities. In the Atlantic, reproduction is mainly by

parthenogenesis Parthenogenesis (; from the Greek + ) is a natural form of asexual reproduction in which the embryo develops directly from an egg without need for fertilization. In animals, parthenogenesis means the development of an embryo from an unfertiliz ...

, with embryos being brooded inside the gastric cavity of their parent, to be liberated as juveniles with limited dispersal ability. This may explain the lack of variability and the rather patchy distribution of this soft coral in the Atlantic as compared to its abundance in the western Mediterranean.

References

External links

* {{Taxonbar, from=Q2349590 Alcyoniidae Cnidarians of the Atlantic Ocean Fauna of the Mediterranean Sea Corals described in 1766 Taxa named by Peter Simon Pallas