Water soluble polymeric 3-alkylpyridinium salts (poly APS; MW 18900 and 5520 Da) were isolated from the marine sponge Raniera sarai. In vitro it strongly inhibited acetyl cholinesterase (AChE) from different species (electric eel, horse serum, human erythrocytes). In our experiments the importance of anti AChE activity in the toxin lethality was evaluated. In vivo experiments were performed on male Wistar rats and ECG, blood pressure and breathing pattern were monitored. After i.v. application of lethal doses of the toxin ECG showed signs of hypo perfusion. Arterial blood pressure fell to mid-circulatory pressure, and breathing stopped after a few breaths At sublethal doses the toxin caused an increase of residual volume, prolongation of expiration, and bradycardia. Patho-anatomical examination revealed that the plugs in lung circulation may cause the death of experimental animals due to cardiorespiratory failure.