Sea stars (Asteroidea) and brittle stars (Ophiuroidea), as well as sea urchins, belong to the Eleutherozoa, a subphylum of echinoderms.
There are about 1,600 species of starfish and about 2,000 species of brittle stars worldwide. Most of these species have five arms. However, there are also species with up to 50 arms. Severed arms usually grow back.
|Related to||Ethinoderms, Eleutherozoa|
|Habitat||Worldwide in the sea|
|Body length||The smallest species (Asterina phylactica) measures 1cm, the largest species (Freyella remex) measures up to over 100cm|
|Food||Varies by species. Mostly they are predatory or eat carrion. However, there are also species that feed on plants.|