nematocyst

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Related to Cnida: nematocyst, Cnidocyst

nem·a·to·cyst

(nem'ă-tō-sist),
A stinging cell of coelenterates consisting of a poison sac and a coiled barbed sting capable of being ejected and penetrating the skin of an animal on contact; of considerable consequence in large jellyfish and in the Portuguese man-of-war which possess large numbers of these stinging cells that can cause great pain and even death.
Synonym(s): cnida, cnidocyst
[nemato- + G. kystis, bladder]

nematocyst

(nĕm′ə-tə-sĭst′, nĭ-măt′ə-)
n.
A capsule within specialized cells in the tentacles of cnidarians, such as jellyfish and corals, containing a barbed, threadlike tube that delivers a toxic sting to predators and prey.

nem′a·to·cys′tic adj.

nematocyst

[nem′ətōsist′]
Etymology: Gk, nema, thread, eidos, form, kystis, bag
a capsule containing a barbed, threadlike process found in certain cells on the external surface of cnidarians, such as the Portuguese man-of-war and jellyfish. The nematocysts of some cnidarians can penetrate the skin and inject a poison, causing painful and potentially fatal injury.

nem·a·to·cyst

(nem'ă-tō-sist)
A stinging cell of coelenterates consisting of a poison sac and a coiled barbed sting capable of being ejected and penetrating the skin of an animal on contact; of considerable consequence in large jellyfish and in the Portuguese man-of-war whose large numbers of these stinging cells can cause great pain and even death.
[nemato- + G. kystis, bladder]

nematocyst

A coiled, tube-like stinging organ of various coelenterates, such as jellyfish. The nematocyst injects a chemical paralyzant.
Nematocystclick for a larger image
Fig. 227 Nematocyst . Nematocysts of Hydra. (a) Discharged. (b) Undischarged.

nematocyst

a structure formed of a hollow thread within a bladder in the CNIDOBLAST or thread cell of COELENTERATES. On stimulation, for example by prey, the thread is everted. Several types exist, such as stinging cells that inject poisonous substances into the prey through the thread, and sticky cells which exude a sticky substance which causes the prey to adhere to the coelenterate tentacle. Enormous numbers are present on the tentacles of some forms and nematocysts are responsible for the jellyfish ‘sting’. Such cells can be utilized by other organisms, for example flatworms preying on coelenterates. The nematocysts migrate to the surface layer of a flatworm which has fed on the coelenterate and are used by the flatworms in exactly the same way as coelenterates use them.