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sea star
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Images & Videos
sunflower starfish high Arctic sea star
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
Crown of thorns starfish (Acanthaster planci). firebrick starfish A bright red starfish with five arms rests on wet rock and green sea grass.
examine a variety of echinoderm species such as starfish, basket star, sand dollar, and sea cucumber
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.
At a Glance
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starfish summary
Quizzes
Sea otter (Enhydra lutris), also called great sea otter, rare, completely marine otter of the northern Pacific, usually found in kelp beds. Floats on back. Looks like sea otter laughing. saltwater otters
Animal Group Names
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sea star: References & Edit History

Article Contributors

Primary Contributors

  • The Editors of Encyclopaedia Britannica
    Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree. They write new content and verify and edit content received from contributors.

Other Encyclopedia Britannica Contributors

Article History

Type Description Contributor Date
Add new Web site: The Royal Society Publishing - Interface - Sea star inspired crawling and bouncing. Oct 15, 2026
Add new Web site: National Park Service - Creature Feature: Sea Stars. Jul 24, 2026
Add new Web site: CORE - An integrated transcriptomic and proteomic analysis of sea star epidermal secretions identifies proteins involved in defense and adhesion (PDF). Feb 06, 2026
Add new Web site: National Center for Biotechnology Information - PubMed Central - Use of Sea Stars to Study Basic Reproductive Processes. Jun 25, 2025
Add new Web site: Cell Press - Current Biology - Cooperative transport in sea star locomotion. May 16, 2025
Add new Web site: Paleontological Research Institution - Digital Atlas of Ancient Life - Asteroidea. Mar 21, 2025
Add new Web site: Frontiers - Frontiers in Microbiology - The Microbial Landscape of Sea Stars and the Anatomical and Interspecies Variability of Their Microbiome. Aug 22, 2024
Add new Web site: Marine Education Society of Australia - Sea stars. Jan 15, 2024
Add new Web site: IndiaNetzone - Starfish. Sep 15, 2023
Add new Web site: National Center for Biotechnology Information - PubMed Central - Use of Sea Stars to Study Basic Reproductive Processes. May 12, 2023
Add new Web site: Animal Diversity Web - Asteroidea. Mar 04, 2023
Add new Web site: National Wildlife Federation - Kids - Sea Star. Apr 07, 2017
Add new Web site: A-Z Animals - Starfish. May 02, 2014
Add new Web site: National Geographic Kids - Animals - Sea Star. Sep 11, 2013
Add new Web site: Animal Planet - Starfish. Sep 11, 2013
"Fission" replaced by "fragmentation." Jul 05, 2011
Photograph of an unnamed Arctic sea star added. Apr 13, 2010
Added new Web site: British Broadcasting Corporation - Common Starfish. Dec 30, 2008
Article revised and updated. Nov 26, 2008
Added new Web site: National Geographic - Animals - Sea Star. Sep 02, 2008
Added new Web site: Enchanted Learning - Sea Star. Mar 07, 2008
Media added. Nov 02, 2006
Article revised. Apr 07, 1999
Article added to new online database. Jul 20, 1998
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