Sea Water Acidification Affects Osmotic Swelling, Regulatory Volume Decrease and Discharge in Nematocytes of the JellyfishPelagia noctiluca

Abstract

Background: Increased acidification/P_CO2 of sea water is a threat to the environment and affects the homeostasis of marine animals. In this study, the effect of sea water pH changes on the osmotic phase (OP), regulatory volume decrease (RVD) and discharge of the jellyfish Pelagia noctiluca (Cnidaria, Scyphozoa) nematocytes, collected from the Strait of Messina (Italy), was assessed. Methods: Isolated nematocytes, suspended in artificial sea water (ASW) with pH 7.65, 6.5 and 4.5, were exposed to hyposmotic ASW of the same pH values and their osmotic response and RVD measured optically in a special flow through chamber. Nematocyte discharge was analyzed in situ in ASW at all three pH values. Results: At normal pH (7.65), nematocytes subjected to hyposmotic shock first expanded osmotically and then regulated their cell volume within 15 min. Exposure to hyposmotic ASW pH 6.5 and 4.5 compromised the OP and reduced or totally abrogated the ensuing RVD, respectively. Acidic pH also significantly reduced the nematocyte discharge response. Conclusion: Data indicate that the homeostasis and function of Cnidarians may be altered by environmental changes such as sea water acidification, thereby validating their use as novel bioindicators for the quality of the marine environment.

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

“…On this basis, we suggest that heavy metals may affect discharge by impairing ion fluxes via membrane transport systems. As stated above, that ion transport in Pelagia noctiluca nematocytes is affected by heavy metals has been already shown [20], pointing out that heavy metals compromise ion fluxes through channels and/or co-transporters needed to perform RVD in isolated nematocytes. On a cellular level, the interaction of heavy metals with cell membrane transport mechanisms is the basis for their effect on biological systems.…”

“…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.…”

“…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. Moreover, in the same species, RVD is also inhibited by heavy metals such as cadmium, zinc and cobalt [19].…”

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

“…These results allowed to conclude that environmental changes can have remarkable effects on homeostasis and function of Cnidarians. 25 Table 1 shows the global data obtained about the activity of some different chemical or physical agents in preventing or promoting nematocyst discharge. Figure 3 shows a discharged nematocyst of Pelagia noctiluca ( Figure 3A), and a particular of the discharged needle ( Figure 3B).…”

Oxidative stress affects responsiveness to hypotonicity of renal cells

“…This homeostatic response has been mostly investigated in mammalian cells such as astrocytes, 11 erythrocytes from different sources, 12 lymphocytes 13 and sperm, 14 but also in cells of lower vertebrates and invertebrates. [15][16][17][18] The series of events leading to RVD has been at least partially defined and consists in loss of intracellular osmolytes followed by a concomitant rapid efflux of intracellular water. Thus, the pivotal counterparts of RVD are: i) ion conducting pathways, mainly permeable to K + , Cl -and organic anions, allowing for the flux of osmolytes out of the cell; and ii) water transporting proteins (AQPs), allowing for the efflux of water along the osmotic gradient.…”