What is a starfish?
Q: What is a starfish?
A: A starfish, or sea star, is an Echinoderm of the Class Asteroidea. They are invertebrates that live in the ocean on the sea floor.
Q: Where do most starfish live?
A: Most starfish live in either deep or shallow water, and some even inhabit the intertidal zone between low and high tide.
Q: How big can they get?
A: The largest species of starfish is the Sunflower Sea Star (Pycnopodia helianthoides), which can have an arm-span of about one metre when fully grown. This is slightly larger than the Crown-of-Thorns Starfish, which lives on coral polyps.
Q: Do they have a skeleton?
A: Yes, although they are invertebrates, starfish do have a kind of skeleton made up of calcium carbonate plates called 'ossicles'. These form their endoskeleton and take on various forms such as spines and granules.
Q: Do they have blood?
A: No, instead of blood, starfish use sea water to pump things around their bodies.
Q: How many species are there?
A: There are over 1500 different species of sea stars.
Q: What do most sea stars eat? A: Most sea stars are predators and feed on mussels, clams, other bivalves and occasionally small fish.
