Paramecium cells possess an osmoregulatory system (ORS) whose H+-ATPase produces a proton gradient which in turn, by chemiosmotic sequestration, allows the rhythmic expulsion of water. This is paralleled by the selective extrusion of some ions, e.g., Ca2+. ORS activity is indeed the dominating component to maintain Ca2+ hoemostasis and it contains an InsP3 receptor probably for Ca2+ fine-tuning. In addition to a complex set of subunits of the H+-ATPase (located in the more peripheral "decorated spongiome") we found, within the frame of the Paramecium genome project, an ORS-specific set of SNAREs (mainly in the "smooth spongiome") and we could localize, with several hot spots, the SNARE-specific chaperone, NSF, to the ORS. Since SNAREs are considered relevant for specific membrane interactions and fusion the question arises whether and how they contribute to the as yet unknown biogenesis of this complex organelle. SNAREs may mediate not only membrane interactions during the rhythmic pulsation activities of the ORS, but SNARE-pins could theoretically also establish the complicated branching of parallel tubular structures in the sponiome. We intend to analyse the complex molecular interactions, incl. cation exchangers and aquaporins, involved in biogenesis and performance of the ORS function in Paramecium.