''Eunicella singularis'', the white gorgonian, is a

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), ...

of colonial soft coral, a

sea fan 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 The following text should be considered a historical, outdated way of treat ...

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 ...

Gorgoniidae Gorgoniidae is a family of soft corals, a member of the subclass Octocorallia in the phylum Cnidaria. Nearly all the genera and species are native to the east and west coasts of America. Characteristics Originally the members of the family Go ...

. It is found in the western

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 ...

Adriatic Sea The Adriatic Sea () is a body of water separating the Italian Peninsula from the Balkans, Balkan Peninsula. The Adriatic is the northernmost arm of the Mediterranean Sea, extending from the Strait of Otranto (where it connects to the Ionian Se ...

and Ionian Sea. It was first described in 1791 by the German naturalist

Eugenius Johann Christoph Esper Eugenius Johann Christoph Esper (2 June 1742 – 27 July 1810) was a German zoologist and naturalist. Born in Wunsiedel in Bavaria, he was professor of zoology at Erlangen university. Life and work Eugen and his brother Friedrich were intro ...

Description

''Eunicella singularis'' can grow to a height of about and a width of . It has a branching structure, growing from a thickened base with a small number of nearly-vertical branches and a few side branches. The surface of the branches is smooth, with the calyces from which the polyps protrude being indistinct. The general colour is white and the polyps are translucent and yellowish-brown or olive.

Distribution and habitat

''Eunicella singularis'' is found in the western

and the

at depths of . It mainly occurs on shallowly sloping rock surfaces which are often partially covered with sediment, but also on pebbles, shells or other objects surrounded by sediment. It favours well-lit locations.

Biology

The polyps of ''Eunicella singularis'' feed by spreading their

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 to intercept

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 organic particles floating past. This diet is supplemented by the energy provided, via

photosynthesis Photosynthesis ( ) is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their metabo ...

, by 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 that are present in the tissues of the sea fan. Reproduction involves the release of

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 A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase ...

e which spend somewhere between a few hours and several days in the open sea. Each larva then settles on the seabed 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 primary polyp within about four days. This founds a new colony and grows by budding off new polyps. The branches increase in length by up to about a year and colonies may live for twenty to thirty years. Predators may feed on the tissues and

epibiont An epibiont (from the Ancient Greek meaning "living on top of") is an organism that lives on the surface of another living organism, called the basibiont ("living underneath"). The interaction between the two organisms is called epibiosis. An ep ...

s such as

bryozoa Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of simple, aquatic animal, aquatic invertebrate animals, nearly all living in sedentary Colony (biology), colonies. Typically about long, they have a spe ...

may take up residence on denuded branches and cause further regression of the living tissues. The colonies may eventually be toppled by currents, perhaps because of the increased resistance to water flow produced by the epibionts. A laboratory study found that at , thermal stress caused the polyps to remain unexpanded (and thus not feeding), respiration was decreased, and photosynthesis stopped (although the symbionts were still present). The sea fan was able to live on its reserves for several weeks during thermal stress before

necrosis Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. The term "necrosis" came about in the mid-19th century and is commonly attributed to German pathologist Rudolf Virchow, who i ...

set in, but it recovered fully when the water temperature fell sufficiently.

Ecology

In the Mediterranean Sea, ''Eunicella singularis'' is often overgrown by the soft coral ''

Alcyonium coralloides ''Alcyonium coralloides'', commonly known as false coral, is a colonial species of soft coral in the family Alcyoniidae. It is native to the northeastern Atlantic Ocean and the Mediterranean Sea. In the former location it generally grows as shee ...

'' which kills the sea fan's soft tissues as it spreads along the branches of its slow-growing

host A host is a person responsible for guests at an event or for providing hospitality during it. Host may also refer to: Places * Host, Pennsylvania, a village in Berks County * Host Island, in the Wilhelm Archipelago, Antarctica People * ...

. The nudibranch ''

Marionia blainvillea ''Marionia blainvillea'' is a species of sea slug, a dendronotid nudibranch, a marine gastropod mollusc in the family Tritoniidae Tritoniidae is a taxonomic family of nudibranchs in the suborder Cladobranchia, shell-less marine gastropod ...

'' feeds on this sea fan and, where their ranges overlap, so does the

whip fan nudibranch ''Duvaucelia odhneri'', is a species of Dendronotida, dendronotid nudibranch. It is a marine (ocean), marine gastropod mollusc in the family (biology), family Tritoniidae. The specific name ''odhneri'' is in honour of Swedish malacologist Nils H ...

(''Tritonia nilsodhneri''). The gastropod mollusc ''

Simnia spelta ''Simnia spelta'' is a species of sea snail, a marine Gastropoda, gastropod Mollusca, mollusc in the Family (biology), family Ovulidae, the ovulids, which are cowrie allies sometimes called "false cowries". It was Species description, first desc ...

'' mimics ''E. singularis'' and feeds and lays its eggs on its branches. The bare areas where the mollusc has removed the

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 ...

tissue soon become colonised by

s such as

algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...

tube worms A tubeworm is any worm-like sessile invertebrate that anchors its tail to an underwater surface and secretes around its body a mineral tube, into which it can withdraw its entire body. Tubeworms are found among the following taxa: * Annelida, the ...

ns, and colonial

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 ...

s. The tissue may regrow and form cavities in which other organisms can flourish, thus forming a small but

biodiverse Biodiversity is the variability of life on Earth. It can be measured on various levels. There is for example genetic variability, species diversity, ecosystem diversity and phylogenetic diversity. Diversity is not distributed evenly on Earth ...

community.

References

External links

* {{Taxonbar, from=Q2684828 Gorgoniidae Fauna of the Mediterranean Sea Animals described in 1791 Taxa named by Eugenius Johann Christoph Esper