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Invertebrate profile

Sea Star

Asteroidea

Sea star is the preferred common name for members of the class Asteroidea; they are echinoderms, not fish. Roughly two thousand described species occupy marine habitats from exposed shores to deep ocean floors, with far more diversity than the familiar five-armed form.

Sea Star in its natural environment
Photo: Bkmiles. CC BY-SA 3.0.
HabitatMarine habitats from tide pools and reefs to sand, seagrass, and the deep sea
DietVaries by species; many are predators or scavengers
RangeOceans worldwide
Signature traittube-footed marine predator

Adaptations

A water vascular system operates rows of tube feet used for movement, attachment, feeding, and sensing. Many species can regenerate damaged arms, but the amount of central body needed and the speed of recovery differ greatly among groups.

Behavior and daily life

Many sea stars move slowly across the bottom while locating shellfish, carrion, coral, or other food. Some predatory species pull bivalve shells slightly apart and extend part of the stomach outside the body to begin digestion.

Conservation

Current profile labelVaries by species

There is no meaningful single status for the entire class. Marine heat waves, sea star wasting disease, collection, pollution, and habitat change can affect particular populations, while other species remain common or poorly studied.

Sea stars move hundreds of tube feet through a water vascular system, using hydraulic pressure rather than muscles alone to extend each foot.

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