sea urchin

From sea +‎ urchin (“hedgehog”), reflecting a similarity in appearance to a hedgehog.

• (General American) enPR: sēʹ ûr'tsĭn, IPA^(key): /ˈsi ˌɝtʃɪ̈n/

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• Hyphenation: sea ur‧chin, sea urchin

sea urchin (plural sea urchins)

1. Any of many marine echinoderms, of the class Echinoidea, commonly found in shallow water, having a complex chewing structure named Aristotle's lantern.
   • 1986, Patrick S. Leahy, Chapter 1: Laboratory Culture of Strongylocentrotus purpuratus Adults, Embryos, and Larvae, Thomas E. Schroeder (editor), Methods in Cell Biology, Volume 27: Echinoderm Gametes and Embryos, page 2,

     Of the many species of sea urchins utilized in biological research today the most widely used in North America is probably the purple sea urchin, Strongylocentrotus purpuratus.

   • 2001, V. L. Kasyanov, Reproductive Strategy of Marine Bivalves and Echinoderms, page 90:

     The pericentriolar radial complex characteristic of the spermatozoa of other echinoderms is lacking in the spermatozoa of all sea urchins.

   • 2004, Belinda J. Sly, The Development and Evolution of the Echinoderm Nervous System, page 9:

     Approximately 20% of sea urchins are direct-developers, meaning that they bypass the pluteal larval stage and develop directly into an adult sea urchin.

• (sea urchin): echinoid

• sand dollar

• echiurans