Sagartia elegans
Encyclopedia
Sagartia elegans is a species of sea anemone
in the family
Sagartiidae
. It is found in coastal areas of northwest Europe at depths down to 50 metres.
having occurred. The column is soft and fleshy and varies in shape, even in one individual, from squat to cylindrical or trumpet shaped, and can grow up to 6 cm (2.4 in) tall. The lower part of the column is somewhat corrugated and there are a number of pale coloured suckers on the upper part to which grit or shell fragments may adhere occasionally. The disc is saucer-shaped with an undulating margin and there are up to 200 tentacle
s arranged irregularly, often arching over the edge. These are mostly about the same length but occasionally there is a much longer one among them. This may be used, as it is in some other sea anemone species, to prevent competing organisms from settling and occupying space nearby. When it is disturbed, a large number of white threads known as acontia
are discharged from cells on the column and from the mouth. These are for defensive purposes and are armed with nematocysts.
When not submerged, S. elegans hangs in a limp fashion. It sometimes partially protrudes the lining of its coelom
through its mouth. If disturbed it will retract more completely, disappearing from view if it is lodged in a crevice.
There are a number of differently coloured varieties:
from Scandinavia
, Iceland
and the North Sea
south to the Mediterranean Sea
. It is common round the coasts of the British Isles
where the form var. miniata is the most abundant. In the Netherlands
the population fluctuates widely, with decreases occurring after severe winters with cold sea temperatures.
and caves. It also favours brightly lit rock walls with fast moving currents.
, scavenger
and predator
. Most of its nourishment comes from the ingestion of small invertebrate
s which are caught by the tentacles and thrust into the mouth. The undigested fragments are later expelled through the mouth.
S. elegans often reproduces asexually
by fragmentation
, also known as basal laceration. As it crawls across a rock surface, pieces of its base become detached and grow into new individuals. This gives rise to groups of sea anemones in close proximity to each other which have identical colourations.
and the soft coral, Alcyonium digitatum
.
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...
. It is found in coastal areas of northwest Europe at depths down to 50 metres.
Description
The base of S. elegans is wider than the column and may reach 3 cm (1.2 in) in diameter. The base is usually anchored to the substrate but can be used as a foot for locomotion. It often has a ragged outline due to fragmentationFragmentation
-In biology:* Fragmentation , a form of asexual reproduction* Fragmentation * Habitat fragmentation* Population fragmentation-Music:* Fragmented , the debut album from the Filipino independent band Up Dharma Down-Other:...
having occurred. The column is soft and fleshy and varies in shape, even in one individual, from squat to cylindrical or trumpet shaped, and can grow up to 6 cm (2.4 in) tall. The lower part of the column is somewhat corrugated and there are a number of pale coloured suckers on the upper part to which grit or shell fragments may adhere occasionally. The disc is saucer-shaped with an undulating margin and there are up to 200 tentacle
Tentacle
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 arranged irregularly, often arching over the edge. These are mostly about the same length but occasionally there is a much longer one among them. This may be used, as it is in some other sea anemone species, to prevent competing organisms from settling and occupying space nearby. When it is disturbed, a large number of white threads known as acontia
Acontia
Acontia is a genus of moths of the Noctuidae family.-Species:* Acontia albida * Acontia albinigra Warren, 1913* Acontia antecedens Walker, 1869* Acontia antica Walker, 1862* Acontia apatelia Swinhoe, 1907...
are discharged from cells on the column and from the mouth. These are for defensive purposes and are armed with nematocysts.
When not submerged, S. elegans hangs in a limp fashion. It sometimes partially protrudes the lining of its coelom
Coelom
The coelom is a fluid-filled cavity formed within the mesoderm. Coeloms developed in triploblasts but were subsequently lost in several lineages. Loss of coelom is correlated with reduction in body size...
through its mouth. If disturbed it will retract more completely, disappearing from view if it is lodged in a crevice.
There are a number of differently coloured varieties:
- Var. miniata: Disc variously coloured and patterned with similar coloured tentacles, often banded.
- Var. rosea: Disc variously coloured and patterned and tentacles rose red.
- Var. aurantiaca: Disc grey and tentacles dull orange.
- Var. nivea: Disc and tentacles translucent white.
- Var. venusta: Disc orange or buff and tentacles white.
Distribution
S. elegans is found in coastal areas of the northeast 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...
from Scandinavia
Scandinavia
Scandinavia is a cultural, historical and ethno-linguistic region in northern Europe that includes the three kingdoms of Denmark, Norway and Sweden, characterized by their common ethno-cultural heritage and language. Modern Norway and Sweden proper are situated on the Scandinavian Peninsula,...
, Iceland
Iceland
Iceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...
and 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...
south to 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 the British Isles
British Isles
The British Isles are a group of islands off the northwest coast of continental Europe that include the islands of Great Britain and Ireland and over six thousand smaller isles. There are two sovereign states located on the islands: the United Kingdom of Great Britain and Northern Ireland and...
where the form var. miniata is the most abundant. In the Netherlands
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...
the population fluctuates widely, with decreases occurring after severe winters with cold sea temperatures.
Habitat
S. elegans is found from the mid-shore down to a depth of about 50 metres. Its base is often in holes and cracks in the rock and it is also found under stones, beneath overhangs, in rock poolsTide 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...
and caves. It also favours brightly lit rock walls with fast moving currents.
Biology
S. elegans is an omnivoreOmnivore
Omnivores are species that eat both plants and animals as their primary food source...
, scavenger
Scavenger
Scavenging is both a carnivorous and herbivorous feeding behavior in which individual scavengers search out dead animal and dead plant biomass on which to feed. The eating of carrion from the same species is referred to as cannibalism. Scavengers play an important role in the ecosystem by...
and predator
Predation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
. Most of its nourishment comes from the ingestion of small invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s which are caught by the tentacles and thrust into the mouth. The undigested fragments are later expelled through the mouth.
S. elegans often reproduces 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 fragmentation
Fragmentation
-In biology:* Fragmentation , a form of asexual reproduction* Fragmentation * Habitat fragmentation* Population fragmentation-Music:* Fragmented , the debut album from the Filipino independent band Up Dharma Down-Other:...
, also known as basal laceration. As it crawls across a rock surface, pieces of its base become detached and grow into new individuals. This gives rise to groups of sea anemones in close proximity to each other which have identical colourations.
Ecology
Other organisms found in the same habitat include the breadcrumb sponge, Halichondria paniceaHalichondria panicea
Halichondria panicea, commonly known as the breadcrumb sponge, is a species of marine demosponge belonging to the family Halichondriidae. This is an abundant sponge of coastal areas of the North Atlantic and the Mediterranean Sea ranging from the intertidal zone to a recorded depth of over 550 m...
and the soft coral, Alcyonium digitatum
Alcyonium digitatum
Alcyonium digitatum or dead man's fingers is a species of soft coral in the Alcyoniidae family. It is found around the coasts of the northern Atlantic Ocean.-Description:...
.