Polar sea star

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Onglets

Description

Distinguishing features

The polar sea star has six arms.

Reproduction

Reproduction takes place externally. The female incubates the eggs by holding them in its arms, held in a characteristic spiral. There is no larval stage in the species of the genus Leptasterias. Males and females are similar in appearance.

Diet

They feed on molluscs, including blue mussels and periwinkles, slow-moving prey and sometimes carrion. They are able to pry apart the shells of bivalve molluscs. The polar sea star digests its prey without swallowing it, by everting its stomach on its prey (i.e. turning its stomach inside out).

Predators

Polar sea stars are eaten by purple sea sun, cod, eider ducks, lobsters and Atlantic wolffish.

Habitat

Polar sea stars are common in the inshore waters of the marine portion of the St. Lawrence, living in the tidal zone at depths of up to 100 m. In our latitudes, they almost completely replace the five-armed common starfish, which lives in a similar, but warmer environment.

Ecology, behaviour

Polar sea stars share their habitat with blue mussels, their favourite prey. The only place where this mollusc can escape the polar sea star is on the dry beach left at low tide twice a day. During the summer, mussels form dense colonies in this area. In the winter, however, they cannot survive the abrasive action of the ice.

French name

Étoile de mer polaire

Scientific name

Leptasterias polaris

Phylum

Echinodermata

Class

Asteroidea

Order

Forcipulata

Family

Plantaginaceae

Size

Diameter: 25 cm

Status

Common species

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