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.
References in periodicals archive ?
Furthermore, all of the variables are measured with error; and measurement error for the X and Y variables is similar ([+ or -] 3% for wet weights and [+ or -]1%-4% for cnida dimensions).
Cnida scaling is described here for the first time.
First and most importantly, cnida scaling is real: larger Anthopleura and Tealia do produce larger spirocysts.
Variation in cnida shape with increasing cnida size
Multiple lines of evidence indicate that cnida shape changes with cnida size.
Taxonomic implications of intraspecific variation in cnida size and shape
Attempts to ascertain cnida function based on numbers of discharged spirocysts and nematocysts retained on targets (e.
We distinguish at least three types of interaction between targets and cnida based on efferent mechanisms: (i) cnida penetration; (ii) cnida adhesion; and (iii) tentacle adherence.
The contribution of each kind of cnida to adhesive force is determined by opposing forces operating on the discharged cnida; one from the tentacle and another from the target.
Factors affecting cnida adhesion are related to the nature of the everted tubule and to the physical and chemical characteristics of the target.
In the present experiments, test probes have been constructed either to maximize or to minimize cnida adhesion.
Passive factors potentially include considerations of the size and shape of the cnida capsules, of the lateral pressure exerted by the adjacent epithelium, as well as any possible cytoskeletal elements, such as the participation of anchoring fibrillar baskets and hemidesmosomal junctions, as occur in hydrozoan nematocytes (Cormier and Hessinger, 1980; Wood and Novak, 1982).