sea urchin


sea urchin

/

Slate-pencil urchin (Heterocentrotus mammillatus)—Douglas Faulkner

Any of about 700 species (class Echinoidea) of echinoderms found worldwide. Sea urchins have a globular body covered with movable, sometimes poisonous, spines up to 12 in. (30 cm) long. Pores along the internal skeleton accommodate slender, extensible, often sucker-tipped tube feet. Sea urchins live on the seafloor and use their tube feet or spines to move about. The mouth is on the body's underside; teeth are extruded to scrape algae and other food from rocks. Some species excavate hiding places in coral, rock, or even steel. Roe of some species is eaten in certain countries.

This entry comes from Encyclopædia Britannica Concise.
For the full entry on sea urchin, visit Britannica.com.

Seen & Heard

What made you look up sea urchin? Please tell us what you were reading, watching or discussing that led you here.

Get Our Free Apps
Voice Search, Favorites,
Word of the Day, and More
Join Us on FB & Twitter
Get the Word of the Day and More