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.

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 ?
The nitric oxide pathway is one pathway in particular that has known involvement in both cnida discharge and muscle contraction effector systems in sea anemones (Salleo et al., 1996; Morrall et al., 2000; Kass-Simon and Pierobon, 2007; Cristino et al., 2008; Anctil, 2009; Colasanti et al., 2010).
Cnida scaling (and the scaling of cellular secretions, generally) may typically reflect the underlying phenomenon of cell scaling.
Here I apply a series of generally conservative and robust statistics to describe and compare data on cnida size as a function of polyp size.
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
Under conditions where cnida adhesion exceeds tentacle adherence, the contribution of each kind of cnida to adhesive force is the product of the number of cnidae discharged and the force required to remove one such cnida from the tentacle (i.e., intrinsic adherence).
Because external calcium is required for cnida discharge in sea anemones (Blanquet, 1970; Lubbock and Amos, 1981; Thorington and Hessinger, 1992; Watson and Hessinger, 1994b), we attempted to inhibit discharge by either pre-treating anemones for 90 min in Ca-free ASW or by following the pre-incubation in Ca-free ASW or ASW with 10% formalin for 5 min at 4 [degrees] C or at room temperature before measuring adhesive force and cnida discharge.
Cnida capsules from anthozoans are prolate ellipsoidal in shape.
Attempts to ascertain cnida function based on numbers of discharged spirocysts and nematocysts retained on targets (e.g., McFarlane and Shelton, 1975) tacitly, but incorrectly, assume that the tentacle adherence for each kind of cnida are equal.
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.