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sea star: Quick Facts

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Facts

Also Known As starfish • Asteroidea

Photos and Videos

sunflower starfish
high Arctic sea star
Crown of thorns starfish (Acanthaster planci).
firebrick starfish
A bright red starfish with five arms rests on wet rock and green sea grass.
Principal features of a starfish. Water for the water vascular system enters through the madreporite and passes into a ring canal and on to radial and lateral canals, from which it enters the tube feet, which are connected to saclike ampullae on top. Contraction of the tube feet forces water into the ampullae, creating suction that allows suckers at the ends of the feet to hold to a surface. When the ampullae contract, water is forced into the feet, extending them and releasing the suction. These coordinated actions permit movement, attachment, and capture of prey. In many starfish, the cardiac stomach is everted through the mouth on the body's undersurface to envelop prey, and digestion may begin outside the body before the stomach is drawn back in.
Study how sieve plates and suction-cupped tube feet enable sea stars to catch prey and move through water
watch a starfish's tube feet pry open a mussel's shell and extrude its stomach onto the mussel
Observe sea star reproduction, from egg and sperm release and fertilization to development of zooplankton embryos and larvae
examine a variety of echinoderm species such as starfish, basket star, sand dollar, and sea cucumber
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