Sagartia troglodytes
Encyclopedia
Sagartia troglodytes is a species
of sea anemone
in the family
Sagartiidae
, also known as the mud sagartia or the cave-dwelling anemone.
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
capital letter "B". 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 (2.5cm) and a length of two inches (5cm) but most specimens are much smaller than this.
, the North Sea
and the Mediterranean Sea
. It is common round the coasts of Britain between the tide marks but is relatively little observed because it is well camouflage
d and is often hidden in cracks, under overhangs, in rock pools
, under seaweed
, among mussel
s or half buried in sand and mud with just its tentacles projecting. In Morecambe Bay
, England
, 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.
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 gonad
s inside the body cavity. The eggs
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
larva which becomes part of the zooplankton
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.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of sea anemone
Sea anemone
Sea anemones are a group of water-dwelling, predatory animals of the order Actiniaria; they are named after the anemone, a terrestrial flower. Sea anemones are classified in the phylum Cnidaria, class Anthozoa, subclass Zoantharia. Anthozoa often have large polyps that allow for digestion of larger...
in the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Sagartiidae
Sagartiidae
Sagartiidae is a family of sea anemones.-Genera:Genera in the family include:* Actinothoe Fischer, 1889* Anthothoe* Bellactis* Botryon* Carcinactis* Cereus Oken, 1815* Choriactis* Gregoria* Habrosanthus...
, 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 tentacleTentacle
A tentacle or bothrium is one of usually two or more elongated flexible organs present in animals, especially invertebrates. The term may also refer to the hairs of the leaves of some insectivorous plants. Usually, tentacles are used for feeding, feeling and grasping. Anatomically, they work like...
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
Latin alphabet
The Latin alphabet, also called the Roman alphabet, is the most recognized alphabet used in the world today. It evolved from a western variety of the Greek alphabet called the Cumaean alphabet, which was adopted and modified by the Etruscans who ruled early Rome...
capital letter "B". 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 (2.5cm) and a length of two inches (5cm) but most specimens are much smaller than this.
Distribution and habitat
S. troglodytes is found in coastal regions of the north east Atlantic OceanAtlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
, the North Sea
North Sea
In the southwest, beyond the Straits of Dover, the North Sea becomes the English Channel connecting to the Atlantic Ocean. In the east, it connects to the Baltic Sea via the Skagerrak and Kattegat, narrow straits that separate Denmark from Norway and Sweden respectively...
and the Mediterranean Sea
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...
. It is common round the coasts of Britain between the tide marks but is relatively little observed because it is well camouflage
Camouflage
Camouflage is a method of concealment that allows an otherwise visible animal, military vehicle, or other object to remain unnoticed, by blending with its environment. Examples include a leopard's spotted coat, the battledress of a modern soldier and a leaf-mimic butterfly...
d and is often hidden in cracks, under overhangs, in rock pools
Tide pool
Tide pools are rocky pools by oceans that are filled with seawater. Many of these pools exist as separate entities only at low tide.Tide pools are habitats of uniquely adaptable animals that have engaged the special attention of naturalists and marine biologists, as well as philosophical...
, under seaweed
Seaweed
Seaweed is a loose, colloquial term encompassing macroscopic, multicellular, benthic marine algae. The term includes some members of the red, brown and green algae...
, among mussel
Mussel
The common name mussel is used for members of several families of clams or bivalvia mollusca, from saltwater and freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, which are often more or less rounded or oval.The...
s or half buried in sand and mud with just its tentacles projecting. In Morecambe Bay
Morecambe Bay
Morecambe Bay is a large bay in northwest England, nearly due east of the Isle of Man and 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 310 km².-Natural features:The rivers Leven,...
, England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
, 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 carnivoreCarnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...
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
Hermaphrodite
In biology, a hermaphrodite is an organism that has reproductive organs normally associated with both male and female sexes.Many taxonomic groups of animals do not have separate sexes. In these groups, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which both...
with gonad
Gonad
The gonad is the organ that makes gametes. The gonads in males are the testes and the gonads in females are the ovaries. The product, gametes, are haploid germ cells. For example, spermatozoon and egg cells are gametes...
s inside the body cavity. The eggs
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
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
Planula
A planula is the free-swimming, flattened, ciliated, bilaterally symmetric larval form of various cnidarian species. The planula forms from the fertilized egg of a medusa, as the case in scyphozoans and some hydrozoans, or from a polyp, as in the case of anthozoans...
larva which becomes part of the zooplankton
Zooplankton
Zooplankton are heterotrophic plankton. Plankton are organisms drifting in oceans, seas, and bodies of fresh water. The word "zooplankton" is derived from the Greek zoon , meaning "animal", and , meaning "wanderer" or "drifter"...
and later settles and develops into a new individual. The species can also reproduce asexually
Asexual reproduction
Asexual reproduction is a mode of reproduction by which offspring arise from a single parent, and inherit the genes of that parent only, it is reproduction which does not involve meiosis, ploidy reduction, or fertilization. A more stringent definition is agamogenesis which is reproduction without...
by the liberation of "ciliated germs" through the walls of the lower column.