Regulatory Volume Decrease (RVD) in nematocytes is affected by crude venom from the jellyfish Pelagia noctiluca (Cnidaria, Scyphozoa)

Crude venom from nematocysts of the Scyphozoan Pelagia noctiluca has been already shown to elicit haemolytic and cytolytic power on cultured cells. The aim of the present work is to assay whether crude venom may also affect Regulatory Volume Decrease under 35 % hyposmotic shock on nematocytes isolated from the Anthozoan Aiptasia mutabilis and here employed as a cell model. For this purpose, crude venom was obtained by sonication of a population of, respectively, 10-25-50 nematocysts/l, while nematocytes were isolated by 605mM NaSCN plus 0.01 mM Ca2+ application on acontia of Aiptasia m. Isolated cells were treated for 30 min with crude venom, checked under a light microscope and submitted to RVD test. Our results show that, under crude venom application, nematocytes were anatomically intact as shown by Trypan blue test, but did not exhibit cell volume regulation with a dose response effect. This effect was reversed by a combined treatment of cells with venom and gramicidine as ionophore, suggesting an inhibitory effect of venom on cell membrane transport mechanisms involved in RVD. Further studies are needed to better ascertain these suggested actions.