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(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.



(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.

References in periodicals archive ?
Evaluation of the effects of various chemicals on discharge of and pain caused by jellyfish nematocysts.
Ultrastructure of a novel eurytele nematocyst of Carybdea alata Reynaud (Cubozoa, Cnidaria).
Nematocyst categories were identified according to the classification of Weill (1934) and Ostman (1988).
The medusa is easily identified by the dichotomously branched tentacles with terminal pads of nematocysts.
Vinegar as a disarming agent to prevent further discharge of the nematocysts of the stinging hydromedusa Olindias sambaquiensis.
Novel role of calcium in exocytosis: mechanism of nematocyst discharge as shown by X-ray microanalysis.
Examination of discharged live nematocysts and comparison with the table of undischarged nematocysts published in Zagal et al.
Slinging nematocysts within the anemone tentacles contain the venom beta phospholipase A2 and are used to stun prey or defend against potential predators (Grotendorst & Hessinger 2000).
In adults, nematocytes were found in clusters, and both networks appeared to have some association with these nematocyst batteries (Fig.
Neurites ran between nematocyst batteries that stained brightly with the tubulin antibodies.
However, hydration may resolve situations such as that described by Gershwin (2006a: 7): "Every effort was made to study inverted and everted nematocysts; however, with fixed material, this was not always possible" improving the quality of nematocyst surveys.