Asterias

Asterias is a genus of echinoderms in the family Asteriidae, comprising several species of sea stars (starfish) found in cold-temperate waters of the Northern Hemisphere. The best-known members are Asterias rubens, the common starfish, and Asterias forbesi; Asterias amurensis is native to the northwestern Pacific and has become an invasive predator in New Zealand.

Members of Asterias typically have five arms radiating from a central disc, with a rough, spiny surface. The underside bears sunken ambulacral grooves with tube feet equipped with suction discs. Coloration varies widely by species and individual.

Habitat and distribution cover rocky shores, seagrass beds, and soft-substrate environments from shallow subtidal zones to modest depths. They are opportunistic feeders, preying on mollusks such as mussels and snails, crustaceans, and other invertebrates, and can also scavenge. They may evert their stomachs to digest prey externally, a hallmark of many starfish feeding strategies.

Life cycle and reproduction are typically sexual, with separate sexes and external fertilization in the water column. Larvae are free-swimming and pass through bipinnaria and brachiolaria stages before developing into juvenile starfish. Some ecological variation exists among species in development and larval duration.

Taxonomically, Asterias is placed in class Asteroidea, order Forcipulatida, and family Asteriidae. The genus name derives from Greek, meaning “star.” Members of Asterias contribute to marine food webs as both predators and prey, and some species have become notable for their ecological impacts when introduced beyond their native ranges.