sea urchin

sea urchin

any echinoderm of the class Echinoidea, such as Echinus esculentus (edible sea urchin), typically having a globular body enclosed in a rigid spiny test and occurring in shallow marine waters

Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005

sea urchin

[′sē ‚ər·chən]

(invertebrate zoology)

A marine echinoderm of the class Echinoidea; the soft internal organs are enclosed in and protected by a test or shell consisting of a number of close-fitting plates beneath the skin.

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Sea Urchin

 

any one invertebrate of the class Echinoidea of the phylum Echinodermata. The body, measuring as much as 30 cm, is covered with rows of skeletal plates that form a shell and bear movable spines and pedicellariae. Sea urchins of the subclass Regularia have a mouth with a masticatory apparatus (Aristotle’s lantern) for scraping algae off rocks. Those of the subclass Irregularia, who feed on detritus, have no masticatory apparatus. Sea urchins are benthic crawling or burrowing animals, moving by means of tube feet and spines. They are dioecious. A stage in their development is the plankton larva, or the echinopluteus; some are viviparous. More than 800 species of sea urchins are extant; there are about 40 species in seas of the USSR. They are widespread in oceans and seas with normal salinity at depths up to 7 km. Some are valuable commercially since the eggs are edible. Fossils of sea urchins have been found in Ordovician deposits.

REFERENCES

Zhizn’ zhivotnykh, vol. 2. Moscow, 1968.
Hyman, L. H. The Invertebrates, vol. 4. New York-London, 1955.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.