''Mesacmaea mitchellii'' is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

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

in the family

Haloclavidae Haloclavidae is a family of sea anemones. Members of the family are found worldwide and many live largely buried in soft substrates with only their oral disc and tentacles protruding. Characteristics Members of this family mostly have elongated ...

. It is found in the northeastern Atlantic Ocean 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 north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the ea ...

where it burrows in soft sediment.

Taxonomy

This species was first described in 1853 by the British naturalist

Philip Henry Gosse Philip Henry Gosse FRS (; 6 April 1810 – 23 August 1888), known to his friends as Henry, was an English naturalist and populariser of natural science, an early improver of the seawater aquarium, and a painstaking innovator in the study of ma ...

as ''Ilyanthus mitchellii''. In 1881, the Italian zoologist

Angelo Andres Angelo "Ginobili" Andres (24 March 1851, Tirano –16 July 1934, Milan) was an Italian Zoology, zoologist. Dr. Angelo Andres studied natural history in Pavia, Leipzig, London and Paris. He became a Professor in Moderna. From 1899–1926 he was di ...

described a new species of sea anemone, ''Mesacmaea stellatus'', and erecting the genus ''

Mesacmaea ''Mesacmaea'' is a genus of sea anemone in the family Haloclavidae. Members of this genus typically burrow into soft substrates. The only part of the animal that is normally visible is the oral disc and tentacles which lie flat on the sand in a s ...

'' to accommodate it. Since then, ''Mesacmaea stellatus'' has been

synonym A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...

ised with ''Ilyanthus mitchellii'', the species becoming ''Mesacmaea mitchellii''. Two other species from the genus '' Ilyanthus'' have also been transferred to the genus ''Mesacmaea''.

Description

''M. mitchellii'' is a robust and distinctive burrowing sea anemone. The column is pear-shaped with a rounded base, and is divided into a scapus, the main part of the column, and a scapulus, a smooth retractile region; the physa, or basal region, is able to adhere firmly to a hard surface but is not normally attached because the animal habitually burrows. The scapus often has sand grains sticking to it. The oral disc bears up to 36

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 in several cycles; the inner cycle contains seven tentacles which tend to be raised above the central mouth while the remaining tentacles are spread widely over the surface of the sediment. The column can be up to across and including the extended tentacles. The scapus is generally reddish, orange or buff, the scapulus is grey, and the oral disc and tentacles are patterned in brown, cream and red. Internally, the pharynx has a single siphonoglyph (ciliated groove) and the

gastrovascular cavity The gastrovascular cavity is the primary organ of digestion and circulation in two major animal phyla: the Coelenterates or cnidarians (including jellyfish and corals) and Platyhelminthes (flatworms). The cavity may be extensively branched into ...

is subdivided by complete

mesenteries In zoology, a mesentery is a membrane inside the body cavity of an animal. The term identifies different structures in different phyla: in vertebrates it is a double fold of the peritoneum enclosing the intestines; in other organisms it forms co ...

, no incomplete mesenteries being present. The retractor muscles are strong.

Distribution and habitat

''Mesacmaea mitchellii'' is native to the northeastern Atlantic Ocean where it occurs in the

sublittoral zone The neritic zone (or sublittoral zone) is the relatively shallow part of the ocean above the drop-off of the continental shelf, approximately in depth. From the point of view of marine biology it forms a relatively stable and well-illuminated ...

around the coasts of Britain and Western Europe and in the Mediterranean Sea. Its depth range is between and its habitat is soft sediment such as sand and gravel. The base of the column is used for burrowing, and the animal feeds with only the top of the column, oral disc and tentacles above the sediment.

References

{{Taxonbar, from=Q2658998 Haloclavidae Animals described in 1853 Cnidarians of the Atlantic Ocean Fauna of the Mediterranean Sea Taxa named by Philip Henry Gosse