The common starfish, common sea star or sugar starfish (''Asterias rubens'') is the most common and familiar

starfish Starfish or sea stars are star-shaped echinoderms belonging to the class Asteroidea (). Common usage frequently finds these names being also applied to ophiuroids, which are correctly referred to as brittle stars or basket stars. Starfish ...

in the north-east

Atlantic 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 an ...

. 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. Genera The World Register of Marine Species lists these genera within the family Asteriidae (in a ...

, 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 ancient Greek, βένθος (bénthos), meaning "t ...

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 unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

(upper) surface of the arms with low, soft mounds called

papula Papulae (sing. papula; also occasionally papulla, papullae), also known as dermal branchiae or skin gills, are projections of the coelom of Asteroidea that serve in respiration and waste removal. Papulae are soft, covered externally with the epi ...

e on either side. The oral (lower) surfaces of the arms have rows of small

tube feet Tube feet (technically podia) are small active tubular projections on the oral face of an echinoderm, whether the arms of a starfish, or the undersides of sea urchins, sand dollars and sea cucumbers; they are more discreet though present on britt ...

, 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 .

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, Norway, Denmark, Germany, the Netherlands and Belgium. An epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian S ...

, 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 north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the ea ...

. It is also known from the western Atlantic where it occurs between

Labrador , nickname = "The Big Land" , etymology = , subdivision_type = Country , subdivision_name = Canada , subdivision_type1 = Province , subdivision_name1 ...

and

Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...

and the

Gulf of Mexico The Gulf of Mexico ( es, Golfo de México) is an oceanic basin, ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of ...

. It is capable of surviving in brackish water.

Ecology

The common starfish feeds on a variety of

organisms. These include

bivalve molluscs Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bival ...

polychaete worms Polychaeta () is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are m ...

barnacle A barnacle is a type of arthropod constituting the subclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in eros ...

s, gastropod molluscs, other

echinoderm An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the sea ...

s and

carrion Carrion () is the decaying flesh of dead animals, including human flesh. Overview Carrion is an important food source for large carnivores and omnivores in most ecosystems. Examples of carrion-eaters (or scavengers) include crows, vultures, c ...

. 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 mussels. Blue mussels are subject to commercial use and intensiv ...

'') and crawl towards it. It can also detect the odour of the predatory

common sunstar The common sunstar 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 distributed from the Arctic down ...

(''Crossaster papposus''), which eats other starfish, and take evasive action. Purple common starfish out for a walk

The common starfish is

dioecious Dioecy (; ; adj. dioecious , ) is a characteristic of a species, meaning that it has distinct individual organisms (unisexual) that produce male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproductio ...

, 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 A water column is a conceptual column of water from the surface of a sea, river or lake to the bottom sediment.Munson, B.H., Axler, R., Hagley C., Host G., Merrick G., Richards C. (2004).Glossary. ''Water on the Web''. University of Minnesota-D ...

. 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 or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Some inse ...

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 (singular: protozoan or protozoon; alternative plural: protozoans) are a group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic tissues and debris. Histo ...

Orchitophrya stellarum ''Orchitophrya stellarum'' is a species of single-celled marine ciliates, a member of the class Oligohymenophorea. It is found living freely in the north Atlantic and Pacific Oceans but is also parasitic, being found inside the gonads of starfish ...

'' 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 the ...

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 ''Asterias forbesi'', commonly known as Forbes sea star, is a species of starfish in the family Asteriidae. It is found in shallow waters in the northwest Atlantic Ocean and the Caribbean Sea. Description left, Underside of ''Asterias forbesi'' ...

'' and ''

Asterias rubens The common starfish, common sea star or sugar starfish (''Asterias rubens'') is the most common and familiar starfish in the north-east Atlantic. Belonging to the family Asteriidae, it has five arms and usually grows to between 10–30 ...

'' during the spring and summer and the winter host may be ''

Leptasterias ''Leptasterias'' is a genus of starfish in the family Asteriidae. Members of this genus are characterised by having six arms although five-armed specimens sometimes occur. ''L. muelleri'' is the type species. The taxonomy of the genus is confus ...

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), also selectively referred to as triterpene glycosides, are bitter-tasting usually toxic plant-derived organic chemicals that have a foamy quality when agitated in water. They are widely distributed ...

-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 gastropod in the family Buccinidae, the "true whelks".Fraussen, K.; Gofas, S. (2014). Buccinum undatum Linnaeus, 1758. Accessed through: World Register of M ...

''), 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 Cleethorpes Pier is a pleasure pier in the town of Cleethorpes, North East Lincolnshire, England. Opened in 1873 on August Bank Holiday, it originally cost £8,000 and was financed by the Manchester, Sheffield and Lincolnshire Railway (later t ...

on the east coast of England along with many

razor shell A razor is a bladed tool primarily used in the removal of body hair through the act of shaving. Kinds of razors include straight razors, safety razors, disposable razors, and electric razors. While the razor has been in existence since before ...

s. 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 and city in the ceremonial county of Hampshire in southern England. The city of Portsmouth has been a unitary authority since 1 April 1997 and is administered by Portsmouth City Council. Portsmouth is the most dens ...

Hampshire Hampshire (, ; abbreviated to Hants) is a ceremonial county, ceremonial and non-metropolitan county, non-metropolitan counties of England, county in western South East England on the coast of the English Channel. Home to two major English citi ...

. 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 food typically consisting of vegetables, sliced cheese or meat, placed on or between slices of bread, or more generally any dish wherein bread serves as a container or wrapper for another food type. The sandwich began as a po ...

in Kent in 2008, and near Brighton ten days later. A similar occurrence occurred on the shore of the

White Sea The White Sea (russian: Белое море, ''Béloye móre''; Karelian and fi, Vienanmeri, lit. Dvina Sea; yrk, Сэрако ямʼ, ''Serako yam'') is a southern inlet of the Barents Sea located on the northwest coast of Russia. It is su ...

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.

References

External links