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The common starfish, common sea star or sugar starfish (''Asterias rubens'') is the most common and familiar
starfish Starfish or sea stars are Star polygon, star-shaped echinoderms belonging to the class (biology), class Asteroidea (). Common usage frequently finds these names being also applied to brittle star, ophiuroids, which are correctly referred to ...
in the north-east
Atlantic The Atlantic Ocean is the second largest of the world's five oceanic divisions, with an area of about . It covers approximately 17% of Earth's surface and about 24% of its water surface area. During the Age of Discovery, it was known for se ...
. Belonging to the family
Asteriidae The Asteriidae are a diverse family of Asteroidea (sea stars) in the order Forcipulatida. It is one of three families in the order Forcipulatida. The oldest unambiguous fossils of the family date to the Late Cretaceous. Genera The World Regi ...
, it has five arms and usually grows to between 10–30 cm across, although larger specimens (up to 52 cm across) are known. The common starfish is usually orange or brownish in color, and sometimes violet; specimens found in deeper waters are pale. The common starfish is found on rocky and gravelly substrates where it feeds on mollusks and other
benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from the Ancient Greek word (), meaning "the depths". ...
invertebrates.


Description

The common starfish normally has five arms, broad at their base and gradually tapering to a point at their tips, which are often turned up slightly. There is a line of short white spines running along the centre of the
aboral Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek language, Greek roots, describe something in its standard anatomical position. Thi ...
(upper) surface of the arms with low, soft mounds called papulae on either side. The oral (lower) surfaces of the arms have rows of small
tube feet Tube or tubes may refer to: * Tube (2003 film), ''Tube'' (2003 film), a 2003 Korean film * "Tubes" (Peter Dale), performer on the Soccer AM#Tubes, Soccer AM television show * Tube (band), a Japanese rock band * Tube & Berger, the alias of dance/e ...
, used in locomotion and feeding. The starfish is usually orange or brick red on the aboral surface and paler on the oral surface but can also be purple or pale brown. Individuals from deep water are usually paler. It grows to a maximum diameter of about but a more normal size is .


Online model organism database

Echinobase is the model organism database for the painted urchin and a number of other echinoderms.


Distribution

The common starfish is native to the northeastern Atlantic Ocean and its range extends from Norway and Sweden, through the
North Sea The North Sea lies between Great Britain, Denmark, Norway, Germany, the Netherlands, Belgium, and France. A sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian Se ...
, round the coasts of Britain, France, Spain and Portugal and southwards along the coasts of Africa to Senegal. It is largely absent from 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 east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern Eur ...
. It is also known from the western Atlantic where it occurs between
Labrador Labrador () is a geographic and cultural region within the Canadian province of Newfoundland and Labrador. It is the primarily continental portion of the province and constitutes 71% of the province's area but is home to only 6% of its populatio ...
and
Florida Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...
and the
Gulf of Mexico The Gulf of Mexico () is an oceanic basin and a marginal sea of the Atlantic Ocean, mostly surrounded by the North American continent. It is bounded on the northeast, north, and northwest by the Gulf Coast of the United States; on the southw ...
. It is capable of surviving in brackish water.


Ecology

The common starfish feeds on a variety of
benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from the Ancient Greek word (), meaning "the depths". ...
organisms. These include
bivalve molluscs Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed by a calcified exoskeleton consis ...
, polychaete worms,
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 ...
s, gastropod molluscs, other
echinoderm An echinoderm () is any animal of the phylum Echinodermata (), which includes starfish, brittle stars, sea urchins, sand dollars and sea cucumbers, as well as the sessile sea lilies or "stone lilies". While bilaterally symmetrical as ...
s and
carrion Carrion (), also known as a carcass, is the decaying flesh of dead animals. Overview Carrion is an important food source for large carnivores and omnivores in most ecosystems. Examples of carrion-eaters (or scavengers) include crows, vultures ...
. When feeding on a mollusc such as a
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 ...
, it attaches its tube feet to each shell valve and exerts force to separate them slightly. Even a gap of just is sufficient for the starfish to insert a fold of its stomach, secrete enzymes and start digesting the mollusc body. When the contents are sufficiently liquid, it brings its stomach back to its rightful position with the food inside. The common starfish has a well-developed sense of smell and can detect the odour of prey species such as the common mussel (''
Mytilus edulis The blue mussel (''Mytilus edulis''), also known as the common mussel, is a medium-sized edible marine (ocean), marine bivalve mollusc in the family (biology), family Mytilidae, the only extant family in the order (biology), order Mytilida, known ...
'') and crawl towards it. It can also detect the odour of the predatory
common sunstar The common sunstar (''Crossaster papposus'') is a species of sea star (aka starfish) belonging to the family Solasteridae. It is found in the northern parts of both the Atlantic and the Pacific Oceans. Distribution The common sunstar is distri ...
(''Crossaster papposus''), which eats other starfish, and take evasive action. The common starfish is
dioecious Dioecy ( ; ; adj. dioecious, ) is a characteristic of certain species that have distinct unisexual individuals, each producing either male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproduction is ...
, which means that each individual is either male or female. In the spring, the females release their eggs into the sea. A moderate sized starfish is estimated to be able to produce 2.5 million eggs. The males shed their sperm and fertilisation takes place 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 larvae are planktonic and drift for about 87 days before settling on 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. Common starfish are believed to live for about seven to eight years. When well fed, the juveniles can increase their radius at the rate of slightly more than per month during the summer and autumn and slightly less than per month in the winter. An adult common starfish can survive starvation for several months although it loses weight in the process. One specimen shrank from a radius of to a radius of after starvation for five months. The
ciliate The ciliates are a group of alveolates characterized by the presence of hair-like organelles called cilia, which are identical in structure to flagellum, eukaryotic flagella, but are in general shorter and present in much larger numbers, with a ...
protozoan Protozoa (: protozoan or protozoon; alternative plural: protozoans) are a polyphyletic group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic debris. Historically ...
'' Orchitophrya stellarum'' is sometimes a parasite of the common starfish. It normally lives on the outer surface of the starfish feeding on sloughed-off epidermal tissue. It appears to become parasitic when the host starfish has ripe gonads and is a male. It enters the starfish through the
gonopore A gonopore, sometimes called a gonadopore, is a genital pore in many invertebrates. Hexapods, including insects, have a single common gonopore, except mayflies, which have a pair of gonopores. More specifically, in the unmodified female, it is ...
s, the orifices where gametes are released. There may be a
pheromone A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavio ...
that alerts it to the fact that the testes are ripe and causes it to change its behaviour. As different species of starfish breed at different times of year, ''Orchitophrya stellarum'' may move from one species to another in accordance with their reproductive cycles. In the Atlantic Ocean, it may alternate between parasitising '' Asterias forbesi'' and '' Asterias rubens'' during the spring and summer and the winter host may be '' Leptasterias spp.''. The ciliate has been found in the testes of all these species. When inside the gonad, it phagocytoses the sperm thus rendering the starfish infertile. Researchers have found a change in the sex ratios of affected populations with fewer males than females being present with the males being consistently smaller than the females. The common starfish produces a
saponin Saponins (Latin ''sapon'', 'soap' + ''-in'', 'one of') are bitter-tasting, usually toxic plant-derived secondary metabolites. They are organic chemicals that become foamy when agitated in water and have high molecular weight. They are present ...
-like substance designed to repel predators, which causes a reaction in the common whelk (''
Buccinum undatum ''Buccinum undatum'', the common whelk or the waved buccinum, is a large, edible Marine (ocean), marine gastropod in the family (biology), family Buccinidae, the "true whelks".Fraussen, K.; Gofas, S. (2014). Buccinum undatum Linnaeus, 1758. Acces ...
''), a common prey species. At dilute concentrations it caused the whelk to take evasive action and at higher concentrations it produced a series of convulsions.


Mass strandings

In January 2013, large numbers of common starfish were washed up near Cleethorpes Pier on the east coast of England along with many razor shells. There were estimated to be four thousand starfish along the stretch of shore. The cause of this mass stranding was unknown but bad weather and storms out at sea coupled with higher than usual tides may have been to blame. During Storm Frank in the early hours of 31 December 2015 hundreds of starfish were stranded along the coast of
Portsmouth Portsmouth ( ) is a port city status in the United Kingdom, city and unitary authority in Hampshire, England. Most of Portsmouth is located on Portsea Island, off the south coast of England in the Solent, making Portsmouth the only city in En ...
,
Hampshire Hampshire (, ; abbreviated to Hants.) is a Ceremonial counties of England, ceremonial county in South East England. It is bordered by Berkshire to the north, Surrey and West Sussex to the east, the Isle of Wight across the Solent to the south, ...
. This is not a unique phenomenon and other mass strandings have occurred in Britain and elsewhere at such places as near
Sandwich A sandwich is a Dish (food), dish typically consisting variously of meat, cheese, sauces, and vegetables used as a filling between slices of bread, or placed atop a slice of bread; or, more generally, any dish in which bread serves as a ''co ...
in Kent in 2008, and near Brighton ten days later. A similar occurrence occurred on the shore of the
White Sea The White Sea (; Karelian language, Karelian and ; ) is a southern inlet of the Barents Sea located on the northwest coast of Russia. It is surrounded by Karelia to the west, the Kola Peninsula to the north, and the Kanin Peninsula to the nort ...
where vast numbers of starfish came ashore on a nine-mile stretch of beach in 2004. It was said that people could not "walk around them because the whole shore was full of starfish". Russian experts expressed mystification as to the cause of the stranding.


See also

* Asterias amurensis


References


External links

* {{Authority control Asteriidae Asterias Echinoderms described in 1758 Taxa named by Carl Linnaeus