''Metridium dianthus'' 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), ...

sea anemone Sea anemones ( ) are a group of predation, predatory marine invertebrates constituting the order (biology), order Actiniaria. Because of their colourful appearance, they are named after the ''Anemone'', a terrestrial flowering plant. Sea anemone ...

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 ...

Metridiidae. It is found in the northern Atlantic Ocean (including the coasts of the

British Isles The British Isles are an archipelago in the Atlantic Ocean, North Atlantic Ocean off the north-western coast of continental Europe, consisting of the islands of Great Britain, Ireland, the Isle of Man, the Inner Hebrides, Inner and Outer Hebr ...

) and in the northeast Pacific Ocean. There is also a record from South Africa, possible resulting from an introduction.

Description

This is the largest sea anemone in the northeastern Atlantic; the smooth column can be in height with a pedal disc wider than this. This form is known as "dianthus" and on a large specimen, the oral disc may have a plume of several thousand tentacles some across, often forming several lobes. A smaller form, found most often in brackish water, is known as "pallidus" and may have two hundred tentacles and be across.

Distribution and habitat

''Metridium dianthus'' is an adaptable, circumboreal species in the

Northern Hemisphere The Northern Hemisphere is the half of Earth that is north of the equator. For other planets in the Solar System, north is defined by humans as being in the same celestial sphere, celestial hemisphere relative to the invariable plane of the Solar ...

. In the eastern Atlantic, its range extends from the

Kola Peninsula The Kola Peninsula (; ) is a peninsula in the extreme northwest of Russia, and one of the largest peninsulas of Europe. Constituting the bulk of the territory of Murmansk Oblast, it lies almost completely inside the Arctic Circle and is border ...

in northern Russia to the

Bay of Biscay The Bay of Biscay ( ) is a gulf of the northeast Atlantic Ocean located south of the Celtic Sea. It lies along the western coast of France from Point Penmarc'h to the Spanish border, and along the northern coast of Spain, extending westward ...

, in the western Atlantic from the Arctic Circle to

Delaware Delaware ( ) is a U.S. state, state in the Mid-Atlantic (United States), Mid-Atlantic and South Atlantic states, South Atlantic regions of the United States. It borders Maryland to its south and west, Pennsylvania to its north, New Jersey ...

, and it also occurs in the northeastern Pacific. It is also present in certain locations where it has probably been introduced, including Patagonia, the Falkland Islands, South Africa and Japan. It occurs at depths down to about , on rocks, in caves, on pebbles, on molluscs such as

mussel Mussel () is the common name used for members of several families of bivalve molluscs, from saltwater and Freshwater bivalve, freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other ...

s, on wharves and jetties, on floating objects, nets and ropes. It tolerates temperatures between and a range of salinities.

Ecology

''Metridium dianthus'' is a suspension feeder, spreading its plume of tentacles and catching small organisms as they float past. These include the eggs and larvae of

molluscs Mollusca is a phylum of protostome, protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant taxon, extant species of molluscs are recognized, making it the second-largest animal phylum ...

polychaete Polychaeta () is a paraphyletic class of generally marine Annelid, annelid worms, common name, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called c ...

s, ascidians,

amphipods Amphipoda () is an order (biology), order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods () range in size from and are mostly detritivores or scavengers. There are more than 10,700 amphip ...

copepod Copepods (; meaning 'oar-feet') are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (living in the water column), some are benthos, benthic (living on the sedimen ...

barnacle Barnacles are arthropods of the subclass (taxonomy), subclass Cirripedia in the subphylum Crustacean, Crustacea. They are related to crabs and lobsters, with similar Nauplius (larva), nauplius larvae. Barnacles are exclusively marine invertebra ...

shrimp A shrimp (: shrimp (American English, US) or shrimps (British English, UK)) is a crustacean with an elongated body and a primarily Aquatic locomotion, swimming mode of locomotion – typically Decapods belonging to the Caridea or Dendrobranchi ...

s and other

crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...

s, as well as

foraminifera Foraminifera ( ; Latin for "hole bearers"; informally called "forams") are unicellular organism, single-celled organisms, members of a phylum or class (biology), class of Rhizarian protists characterized by streaming granular Ectoplasm (cell bio ...

and

diatom A diatom (Neo-Latin ''diatoma'') is any member of a large group comprising several Genus, genera of algae, specifically microalgae, found in the oceans, waterways and soils of the world. Living diatoms make up a significant portion of Earth's B ...

s. When there is either too strong a current, or very little water movement, it can retract both the plume of tentacles and the column. The sexes are separate in this species and, in Scotland, spawning takes place in June and July. Batches of eggs are emitted by the female at intervals of two to ten days, not through the siphonoglyphs, as might be expected, but through slits in the body wall known as cinclides. The eggs sink to the seabed and are fertilised in the

water column The (oceanic) water column is a concept used in oceanography to describe the physical (temperature, salinity, light penetration) and chemical ( pH, dissolved oxygen, nutrient salts) characteristics of seawater at different depths for a defined ...

. The planula larvae are

plankton Plankton are the diverse collection of organisms that drift in Hydrosphere, water (or atmosphere, air) but are unable to actively propel themselves against ocean current, currents (or wind). The individual organisms constituting plankton are ca ...

ic, before sinking to the seabed and undergoing

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 juveniles.

References

{{Taxonbar, from=Q2106352 Metridiidae Cnidarians of the Atlantic Ocean Cnidarians of the Pacific Ocean Animals described in 1768