Nematocyst

nematocyst

[nə′mad·ə‚sist]

(invertebrate zoology)

An intracellular effector organelle in the form of a coiled tube which may be rapidly everted in food gathering or defense by cnidarians.

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 It might be outdated or ideologically biased.

Nematocyst

 

(also stinging cell, nettling cell), a unique cell in the ectoderm and endoderm of most coelenterates (with the exception of ctenophorans) whose function is to attack prey and protect against enemies. A nematocyst contains a thin-walled capsule whose cavity contains a spirally coiled thread. The nucleus is situated at the base of the cell. A nematocyst has a sensory extension called a cnidocil projecting from the surface. When stimulated chemically or mechanically, the cnidocil forcefully ejects a straight, untwisted thread into the prey’s body. The sting kills small animals and sometimes causes painful burns and even death in large animals. A nematocyst can be used only once, after which it is discarded and replaced by a new one formed with specialized cells.

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