Discharge Mechanism of the Nematocysts of Pelagia noctiluca
The nematocysts are complex organelles, contained in specialized cells, the nematocytes. Under adequate stimulus (Lubbock 1979; Tardent et al. 1980; Ertman and Davenport 1981) the nematocysts eject a threat that, in turn, either adheres to or penetrates into the prey, injecting the venomous substances contained into the capsule fluid. The nematocyst is generally believed to be formed as a secretory product of Golgi apparatus (Cormier and Hessinger 1980) although such an interpretation has been recently questioned (Holstein 1981). The complex process of differentiation which produces the three layers of the capsule wall and the thread has been recently described by Holstein (1981). The cnidocil apparatus seems to be the sensory receptor that elicits the discharge in the intact system in situ (Cormier and Hessinger 1980). Nevertheless, the discharging capacity is retained in isolated nematocysts, although it is less prompt than it is in situ. Since quantitative and detailed data concerning the effectiveness of stimuli cannot be obtained on nematocysts in situ, isolated capsules are frequently employed with the aim to investigate the mechanism of discharge, which, in spite of the numerous attempts to elucidate it, is still uncertain.
KeywordsMethylene Blue Discharge Capacity Neutral Salt Capsule Wall Polyvalent Cation
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