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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 ?
Despite popular belief, chemicals such as alcohol, meat tenderiser, ammonia or baking soda should not be applied, as they only encourage more discharge by the nematocysts.
Avoid using fresh water; it's hypotonic and will cause the remaining nematocysts to fire into the skin.
It is not known as a toxic animal, yet it does contain nematocysts capable of catching prey.
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.
A sea anemone eats prey that it catches with its stinging nematocysts, which paralyze prey.
It lives around the surface of warm ocean waters throughout the world, and can cause painful stings if its tentacles come into contact with human flesh and release its nematocysts.
During this process, the snails may be continually exposed to discharging nematocysts.
The stickiness is caused by tiny stinging cells called nematocysts (NEM-uh-tuh-sists) lining the sides of the tentacles.
The solution immediately and completely eliminates the pain from a sting while also neutralizing any nematocysts left on the skin when a jellyfish tentacle comes into contact with flesh.
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).