''Sagartia troglodytes'' 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 ...

of sea anemone in the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Sagartiidae, also known as the mud sagartia or the cave-dwelling anemone.

Description

The base is anchored in holes in the rock and is a little wider than the column. This is smooth and firm, extending to a length several times its width, and covered in sticky suckers on its upper part. The usually flat oral disc is finely patterned and surrounded by four or five rings of numerous short

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 ma ...

s, the longest ones being nearest the mouth. This is raised on a slight mound at the centre of the disc. The general colour is varying sombre shade of olive green or brown with vertical striations on the column. The radial striations on the oral disc are finely patterned in grey, white and black and the tentacles are translucent and banded in white and grey. At the base of each tentacle there is a distinctive black mark shaped like a

Roman Roman or Romans most often refers to: *Rome, the capital city of Italy *Ancient Rome, Roman civilization from 8th century BC to 5th century AD *Roman people, the people of ancient Rome *'' Epistle to the Romans'', shortened to ''Romans'', a lette ...

capital letter "B".''Sagartia troglodytes''

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 ...

. A history of the British sea-anemones and corals. Retrieved 2011-09-03. Pieces of gravel and fragments of shell are often stuck to the upper part of the column. In size, the column can grow to a diameter of an inch (2.5 cm) and a length of two inches (5 cm) but most specimens are much smaller than this.John Barrett & C. M. Young (1958). Collins Pocket Guide to the Sea Shore. p. 59.

Distribution and habitat

''S. troglodytes'' is found in coastal regions of the north east

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...

, the

North Sea The North Sea lies between Great Britain, Norway, Denmark, Germany, the Netherlands and Belgium. An epeiric sea, epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and 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 north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the ...

. It is common round the coasts of Britain between the tide marks but is relatively little observed because it is well

camouflage Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard's spotted coat, the b ...

d and is often hidden in cracks, under overhangs, in rock pools, under seaweed, among mussels or half buried in sand and mud with just its tentacles projecting. In

Morecambe Bay Morecambe Bay is a large estuary in northwest England, just to the south of the Lake District National Park. It is the largest expanse of intertidal mudflats and sand in the United Kingdom, covering a total area of . In 1974, the second larges ...

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...

, it is found anchored to stones buried several inches beneath the surface of this expanse of mudflats, or sometimes not even attached at all but living freely. It can retract into a spherical form when disturbed and no longer be visible from the surface.

Biology

Like other sea anemones, ''S. troglodytes'' is a

carnivore A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other s ...

and feeds on small invertebrates which it traps with its tentacles and channels into its mouth. Any undigested pieces are expelled from the mouth over the period of a few hours or days. ''S. troglodytes'' is a hermaphrodite with gonads inside the body cavity. The

eggs Humans and human ancestors have scavenged and eaten animal eggs for millions of years. Humans in Southeast Asia had domesticated chickens and harvested their eggs for food by 1,500 BCE. The most widely consumed eggs are those of fowl, especial ...

are discharged from the mouth, being wafted out individually by cilia on the tentacles. The sperm are produced separately also emanating from the mouth when they give the appearance of a white plume being liberated into the water column. The fertilised egg 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. Some groups of Nemerteans also produce larvae that are very similar to the planula, which ...

larva which becomes part of the

zooplankton Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...

and later settles and develops into a new individual. The species can also reproduce asexually by the liberation of "ciliated germs" through the walls of the lower column.

References

{{Taxonbar, from=Q2341847 Sagartiidae Cnidarians of the Atlantic Ocean Fauna of the Mediterranean Sea Animals described in 1847