Nematocysts

Mariscal, Richard N.

doi:10.1016/b978-0-12-512150-7.50008-6

Cited by 302 publications

(233 citation statements)

References 176 publications

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“…Nematocysts of various cnidarians contain large amounts of polypeptides rich in glutamic and aspartic acids (Blanquet 1970;Mariscal 1974) including poly-c-glutamic acid (pG) (Weber 1990). In stenoteles of Hydra, Weber (1989) found a glutamic acid monomer concentration of about 2 M (chain length of the polymer about 20 units).…”

Section: Discussionmentioning

confidence: 99%

Formation and discharge of nematocysts is controlled by a proton gradient across the cyst membrane

Berking

Herrmann

2005

Helgol Mar Res

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Cnidaria catch and kill their prey by means of nematocysts. A nematocyst consists of a capsule containing a coiled tubule. On triggering, the cyst extrudes this tubule in an extremely rapid manner. The mechanisms and driving forces of discharge are still unknown. We found nematocysts of various cnidarians to be acidic inside and propose that the pH difference between cyst matrix and cytoplasm drives the discharge of cysts. For large cysts of Aiptasia we calculated that the internal concentration of protons and protonated carboxyl groups is about 5 M. Cysts contain polyacids in a high concentration. At a low pH several of the carboxyl groups of the polymer are uncharged. The carboxyl groups dissociate when, on triggering, the proton concentration becomes balanced across the cyst membrane. The speed of protons in water is extremely rapid. Thus, the equilibration of the proton concentration initially results in a negative net charge within the cyst and therefore in a sudden electrostatic repulsion between the dissociated carboxyl groups of the polymer. This causes an increase in the pressure of the matrix against the cyst wall. We suggest that this nonosmotic pressure increase causes the first and extremely rapid step of discharge. We propose that in a second step cations and water are taken up, generating an increase in osmotic pressure. A change in the pH value may also facilitate the invagination and evagination, respectively, of the tubule.

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Section: Discussionmentioning

confidence: 99%

Formation and discharge of nematocysts is controlled by a proton gradient across the cyst membrane

Berking

Herrmann

2005

Helgol Mar Res

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“…Nematocysts were identified according to the classification system of Weill (1934) with modifications made by Carlgren (1940Carlgren ( , 1945, Cutress (1955), Mariscal (1974), Calder (1977 and Östman (2000). The nematocyst nomenclature is that of Watson and Wood (1988) and Östman (2000).…”

Section: Nomenclature and Nematocysts Studiedmentioning

confidence: 99%

Acontia and mesentery nematocysts of the sea anemone <i>Metridium senile</i> (Linnaeus, 1761) (Cnidaria: Anthozoa)

Östman¹,

Kultima²,

Roat³

et al. 2010

Sci. Mar.

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“…Nematocysts are diverse in structure and interactions with target tissues (Mariscal, 1974;Williamson et al, 1996). The nematocyst itself consists of an intracellular capsule containing a tightly coiled and folded tubule.…”

Section: Introductionmentioning

confidence: 99%

Functional characteristics of nematocysts found on the scyphomedusa Cyanea capillata

Colin

Costello

2007

Journal of Experimental Marine Biology and Ecology

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Although prey capture by cnidarians is mediated through nematocysts, their influence on prey selection by cnidarians remains poorly documented. The difficulty in visualizing nematocyst-prey interactions remains the chief obstacle to understanding how the wide variety of nematocyst types influences the mechanics of prey capture. One solution to this limitation has been to assign functional roles to nematocysts based on morphological characters of discharged cnidae. Here we report results of an alternative approach based upon dynamic traits of nematocyst discharge. We examined tubule lengths, tubule discharge velocities and net-togross displacement ratios of tubules of discharging nematocysts possessed by the cosmopolitan scyphomedusa, Cyanea capillata. This nematocyst assemblage consisted of euryteles, birhopaloids and three different isorhizas -a-isorhizas, A-isorhizas and Oisorhizas. Dynamic traits varied little within each nematocyst type but there were significant differences between the different types. Most importantly, dynamic traits varied significantly within a broad category of nematocyst -the isorhizas -indicating that conventional classification schemes that infer function based on broad nematocyst categories may not appropriately describe the functional roles of these nematocysts. The dynamic properties of discharging nematocysts were consistent with physical results described in studies using scanning electron microscopy images of nematocyst-prey interactions. These data suggest that nematocysts vary significantly in their roles during predation, but that inferences relating prey selection with broad nematocyst categories merit careful examination.

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Nematocysts

Cited by 302 publications

References 176 publications

Formation and discharge of nematocysts is controlled by a proton gradient across the cyst membrane

Formation and discharge of nematocysts is controlled by a proton gradient across the cyst membrane

Acontia and mesentery nematocysts of the sea anemone <i>Metridium senile</i> (Linnaeus, 1761) (Cnidaria: Anthozoa)

Functional characteristics of nematocysts found on the scyphomedusa Cyanea capillata

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