''Leptasterias muelleri'', the northern starfish, 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 ...

of starfish in the

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

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 is found in the

Arctic Ocean The Arctic Ocean is the smallest and shallowest of the world's five major oceans. It spans an area of approximately and is known as the coldest of all the oceans. The International Hydrographic Organization (IHO) recognizes it as an ocean, a ...

and the northern

Atlantic Ocean 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 ...

. It is a

predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...

and scavenger and is unusual among starfish in that it broods its young.

Description

''Leptasterias muelleri'' is a small starfish which is often about in diameter but can grow to . It has a small disc and five broad, tapering arms that are clearly demarcated from the disc. The aboral (upper) surface is rough, being covered with longitudinally arranged, knob-shaped spines. These are surrounded by small

pedicellariae A pedicellaria (plural: pedicellariae) is a small wrench- or claw-shaped appendage with movable jaws, called valves, commonly found on echinoderms (phylum Echinodermata), particularly in sea stars (class Asteroidea) and sea urchins (class Echinoi ...

(claw-shaped structures) and interspersed by

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 epid ...

e (respiratory projections). The oral (under) surface of the arms have four longitudinal rows of

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 br ...

with suckers. The colour of this starfish may be pale purple, pink or green, with pale coloured tips to the arms. Green individuals have a symbiotic green alga living in the tissues and are normally found living in shallow water.

Distribution and habitat

''Leptasterias muelleri'' has a wide distribution in the Arctic Ocean and northern Atlantic Ocean. Its range extends from the Gulf of Maine, Greenland and Iceland to the Barents Sea, Scandinavia, the North Sea and the British Isles. It occurs on the lower shore, where it hides under stones, and to depths of at least .

References

{{Taxonbar, from=Q2407614 Leptasterias Animals described in 1846 Taxa named by Michael Sars