page_title: Starfish
hierarchical_section_title: Starfish
caption_attribution_description: Ochre sea star from Olympic National Park, USA, taken June 2003. Kodak PhotoCD image from 35mm film camera.
context_page_description: Starfish, or sea stars, are Echinoderms of the Class Asteroidea.ᵖ³⁵
  All live in the ocean, on the sea floor. Many starfish live in deep water, others in shallow water. Some live in the intertidal zone, between low and high tide. They have five or more arms and can be quite large. The Sunflower sea star is the largest: fully grown, its arm-span is about a metre. This is a bit larger than the famous Crown-of-thorns starfish, which lives on coral polyps.
  Although starfish are invertebrates, they do have a kind of skeleton. The bodies of starfish are composed of calcium carbonate plates, known as 'ossicles'. These form the endoskeleton, which takes on a variety of forms such as spines and granules.
  They have a primitive nervous system, but not a brain. They also do not have blood, instead they use sea water to pump things around their bodies.
  There are over 1500 different species of sea star. Most sea stars are predators. They eat mussels, clams, and other bivalves. Occasionally, they catch small fish.
context_section_description: Starfish, or sea stars, are Echinoderms of the Class Asteroidea.ᵖ³⁵
  All live in the ocean, on the sea floor. Many starfish live in deep water, others in shallow water. Some live in the intertidal zone, between low and high tide. They have five or more arms and can be quite large. The Sunflower sea star (Pycnopodia helianthoides) is the largest: fully grown, its arm-span is about a metre. This is a bit larger than the famous Crown-of-thorns starfish, which lives on coral polyps.
  Although starfish are invertebrates, they do have a kind of skeleton. The bodies of starfish are composed of calcium carbonate plates, known as 'ossicles'. These form the endoskeleton, which takes on a variety of forms such as spines and granules.
  They have a primitive nervous system, but not a brain. They also do not have blood, instead they use sea water to pump things around their bodies.
  There are over 1500 different species of sea star. Most sea stars are predators. They eat mussels, clams, and other bivalves. Occasionally, they catch small fish.
caption: Starfish on beach: about 25 cm (10 inches) in size
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