Sea stars shed their eggs and sperm into the water, and fertilization occurs externally, producing a swimming, bilaterally symmetrical larva. The larva settles and undergoes a sessile (attached) period while metamorphosing into the free-living, radially symmetrical adult form. A single female may produce over 2 million eggs in one spawn, but the eggs and larvae form part of the plankton on which many marine animals feed, and few survive.
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The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.
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