''Leptasterias polaris'', the polar six-rayed star, 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 ...

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

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

Asteriidae. It is found in cold waters in the northwest Atlantic Ocean and in polar regions.

Description

''Leptasterias polaris'' is a small, slow growing, compact starfish with six arms. The aboral (upper) surface has a covering of blunt spiny plates and is usually some shade of brown or grey.

Distribution and habitat

''Leptasterias polaris'' occurs in the north west Atlantic Ocean from the

Gulf of Maine The Gulf of Maine is a large gulf of the Atlantic Ocean on the east coast of North America. It is bounded by Cape Cod at the eastern tip of Massachusetts in the southwest and by Cape Sable Island at the southern tip of Nova Scotia in the northeast ...

northwards, and in Arctic waters. It has also been found in the

Azores ) , motto =( en, "Rather die free than subjected in peace") , anthem= ( en, "Anthem of the Azores") , image_map=Locator_map_of_Azores_in_EU.svg , map_alt=Location of the Azores within the European Union , map_caption=Location of the Azores wi ...

and European waters.

Biology

''Leptasterias polaris'' is a major predator in the cold waters in which it lives. Young individuals are mostly found on rocks less than deep and feed on such

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 ...

as the blue mussel ('' Mytilus edulis'') and ''

Hiatella arctica ''Hiatella arctica'', known as the wrinkled rock-borer, the arctic hiatella or the arctic saxicave, is a species of saltwater clam, a marine bivalve mollusc in the family Hiatellidae. The white shell of this mollusc is thick and more or less r ...

''. Older individuals move to deeper waters where the seabed is sand or mud and feed on clams such as the Greenland cockle (''

Serripes groenlandicus ''Serripes groenlandicus'', the Greenland cockle, is a species of bivalve mollusc in the family Cardiidae. It can be found along the Atlantic coast of North America, ranging from Greenland to Cape Cod, as well as along the Pacific coast, from Ala ...

''), '' Spisula polynyma'', the blunt gaper (''

Mya truncata ''Mya truncata'', common name the blunt gaper or truncate softshell, is a species of edible saltwater clam, a marine bivalve mollusk in the family Myidae. Description Shells of ''Mya truncata'' can reach a size of about . These bivalves are s ...

'') and the Atlantic jackknife clam (''

Ensis directus The Atlantic jackknife clam, ''Ensis leei'', also known as the bamboo clam, American jackknife clam or razor clam, is a large edible Marine (ocean), marine bivalve mollusc found on the North American Atlantic Ocean, Atlantic coast, from Canada t ...

'') which they dig up with their tube feet. They also eat gastropod molluscs such as 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 ...

'') and the American pelicanfoot (''

Arrhoges occidentalis ''Arrhoges occidentalis'', common name the American pelicanfoot, is a species of medium-sized sea snail, a marine gastropod mollusk in the family Aporrhaidae, the pelican's foot snails or pelican's foot shells. Morton (1956) considers ''Ar ...

''). In a laboratory study it was found that the starfish detected their prey by odours in the water. Hungry starfish which had not fed for two months, worked their way across the current until their olfactory tube feet, located near the tips of their arms, smelt an edible prey item after which they begin to travel up-current towards the source of the odour. Moving upstream in this way had the advantage that the prey was less likely to detect the approach of the starfish. Well fed starfish wandered in a more random fashion. Breeding takes place when the water temperature falls to about and the day length is at its minimum. Over a period of seven to eight weeks the normally solitary starfish begin to aggregate, eventually some climbing on top of others. The males release sperm which accumulates in a layer on the seabed and the females later release their eggs on top. The females brood the developing eggs for four months but that is probably more to keep them clean and healthy and prevent predation than to speed their development as unbrooded eggs were found in the laboratory to develop at the same rate as brooded ones.

References

{{Taxonbar, from=Q2272589 Leptasterias Starfish described in 1842