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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 ?
Avoid using fresh water; it's hypotonic and will cause the remaining nematocysts to fire into the skin.
Some evidence suggests that the use of a sunscreen may actually protect skin from penetration by the nematocysts.
Two species of nematocysts in Campanulariidae (Cnidaria, Hydrozoa) studied by light and scanning electron microscopy.
The clownfish are immune to the nematocysts on the anemones' tentacles as their skin has a special covering.
But a chosen few creatures such as anemonefish, also often called clownfish, nestle within the tentacles without being harmed by their toxin-filled capsules, called nematocysts.
These hyperplastic stolons proliferate, and as they do,they swell by recruiting large numbers of nematocysts (Buss et al.
Its relatively powerful stinging nematocysts are responsible for intense burning reactions among swimmers and those who must work around the water.
Welcome to the world of cnidarians--a family of sea anemones, jellyfish and other marine invertebrates that kill their enemies and prey by firing poisonous, microscopic projectiles called nematocysts.
The tentacles contain nematocysts, a group of nasty little cells that can eject a toxin-carrying harpoon in a fraction of a second.
Medusa: width 4-5 mm across extended tentacles, umbrella flattened hemispherical, oral surface more or less six-sided with thickened marginal ring packed with nematocysts.
Vinegar as a disarming agent to prevent further discharge of the nematocysts of the stinging hydromedusa Olindias sambaquiensis.