Asteroidea  

Invertebrates close-up never fail to please: with their bright colors and strange structures, they begin to take on patterns that are more art than animal...

Except for a few species which inhabit brackish waters, asteroids are benthic organisms found in marine environments.

Habitat Regions: saltwater or marine

Aquatic Biomes: brackish water

Other Habitat Features: intertidal or littoral

Asteroids are mainly scavengers and carnivores. In many areas where they are found they are high level predators. Asteroids feed on slow moving prey, including gastropods, bivalves, barnacles, polychaetes and other invertebrates. They feed by grasping the prey, then everting their stomach and secreting primary enzymes on the prey. The digestive juices break down the tissue of the prey, which the asteroids then suck up.

Some asteroids are suspension feeders. Plankton and organic detritus sticks to mucus on the body surface and is moved by cilia to the mouth. A few species that use their pedicellariae to capture prey may even feed on fish.

Asteroids have a complete digestive system. The mouth leads to the cardiac stomach, which is what the sea star everts to digest its prey. The cardiac stomach leads to a pyloric stomach. Digestive glands, or pyloric ceca located in each arm. Enzymes are secreted through pyloric ducts. A short intestine follows the pyloric stomach and leads to the anus.

Foraging Behavior: filter-feeding

Primary Diet: carnivore (Piscivore , Eats non-insect arthropods, Molluscivore , Scavenger )

Some asteroids, such as Acanthaster planci, have increased in population and damage coral reefs as a result of their grazing. Many asteroids are top predators and keystone species.

Ecosystem Impact: keystone species