Nematocytes’ activation in Pelagia noctiluca (Cnidaria, Scyphozoa) oral arms

Abstract

Nematocytes' discharge is triggered to perform both defense and predation strategies in cnidarians and occurs under chemico-physical stimulation. In this study, different compounds such as amino acids and proteins (mucin, albumin, poly-L: -lysine, trypsin), sugars and N-acetylate sugars (N-acetyl neuraminic acid, N-acetyl galactosamine, sucrose, glucose, agarose and trehalose), nucleotides (ATP and cAMP), were tested as chemosensitizers of nematocyte discharge in the oral arms of the scyphozoan Pelagia noctiluca, particularly abundant in the Strait of Messina (Italy). Excised oral arms were submitted to a combined chemico-physical stimulation by treatment with different compounds followed by mechanical stimulation by a non-vibrating test probe. Discharge induced by a chemico-physical stimulation was more significant than that obtained after mechanical stimulation alone. A chemosensitizing mechanism, with a dose-dependent effect, was observed after treatment with sugars, amino compounds such as glutathione, nucleotides and mucin, according to that already seen in sea anemones. Such findings suggest that, though Anthozoa and Scyphozoa exhibit different divergence times during the evolutionary process, the discharge activation exhibits common features, probably derived from their last common ancestor.

The venom and the toxicity of Pelagia noctiluca (Cnidaria: Scyphozoa). A review of three decades of research in Italian laboratories and future perspectives

“…Notably, the chemosensitizing effect of sugars, glutathione, nucleotides and mucin was dosedependent effect. 22 More recent research 23 reported the evaluation of the activity of local anesthetic lidocaine, alcohols, acetic acid and ammonia in preventing discharge of Pelagia noctiluca nematocysts when induced by chemosensitizers (N-acetyl neuraminic acid, N-acetyl galactosamine, glutamate, artherenol, carbachol, arginine, glycine, cysteine, mucin, albumin). Excluding lidocaine which induced a slight, non significant, increase of discharge in comparison to the control, all evaluated compounds failed to induce discharge per se and, furthermore, they were able to impair the discharge induced by chemosensitizers.…”

“…The discharging resulted more efficient with the combined activity of both mechanical and chemical stimuli and a dose-dependent chemosensitizing mechanism was observed after treatment with nucleotides, mucin, sugars, and glutathione. 22 Finally, in studies on the effect of pH changes on the osmotic phase (OP), regulatory volume decrease (RVD) and nematocyte discharge, Pelagia noctiluca nematocysts subjected to hyposmotic shock were seen to expand osmotically and then to regulate the volume within 15 min at pH 7.65. On the contrary, acidic values compromised the OP (pH=6.5), reduced or abrogated RVD (pH=4.5), and reduced discharge.…”

Heavy Metals Affect Nematocysts Discharge Response and Biological Activity of Crude Venom in the JellyfishPelagia noctiluca(Cnidaria, Scyphozoa)

“…When an appropriate chemico-physical stimulus is applied, both tubule and toxins are promptly delivered via an exocytotic process termed discharge. Discharge is one of the most rapid biological responses known so far, whose activation mechanism has been focused on by many authors [2,3,4,5]. The first stage for discharge activation is chemosensitization, occurring via binding of exogenous compounds to chemoreceptors located on cells, other than nematocytes, modulating in turn the mechanosensitive apparatus (cilia).…”

“…The current knowledge of Pelagia noctiluca biology [17,28] and physiology [5,29,30] may allow to propose this specimen and its homeostatic features as new models to monitor the possible presence and ecological impact of marine pollutants, such as hydrocharbons and heavy metals, and ocean acidification. Concerning this latter phenomenon, it has been recently proven that acidification of the external medium significantly impairs discharge response and cell volume regulation capability following hypotonic shock (regulatory volume decrease, RVD) [20] of Pelagia noctiluca nematocytes.…”

“…With regard to discharge response and biological activity of crude venom in the jellyfish Pelagia noctiluca , several investigations added novel contribution to the understanding of the physiology of this Cnidarian [4,5,19,20,21,22,23,24,25,26,27]. The current knowledge of Pelagia noctiluca biology [17,28] and physiology [5,29,30] may allow to propose this specimen and its homeostatic features as new models to monitor the possible presence and ecological impact of marine pollutants, such as hydrocharbons and heavy metals, and ocean acidification.…”