INHIBITORY EFFECTS OF EXTRACTS FROM THE MARINE ALGA CAULERPA-TAXIFOLIA AND OF TOXIN FROM CAULERPA-RACEMOSA ON MULTIXENOBIOTIC RESISTANCE INTHE MARINE SPONGE GEODIA-CYDONIUM

The invasive growth of the introduced green alga Caulerpa taxifolia, a lready affecting the richness and diversify of the littoral ecosystems , has become a major ecological problem in the Mediterranean Sea. Prev iously, we demonstrated that the water pollutant tributyltin induces a poptosis in tissue of the marine sponge Geodia cydonium at concentrati ons of 3 mu M and higher. Here we show that exposure of G. cydonium to low (non-toxic) concentrations of Cauierpa extract or purified cauler pin (10 mu g/ml) together with low doses of tributyltin (1 mu M; non-t oxic), results in a strong apoptotic effect. Evidence is presented tha t the enhancement of toxicity of tributyltin by Caulerpa extract is at least partially caused by inhibition of the multixenobiotic resistanc e (MXR) pump by the algal toxin. Caulerpa extract, as well as caulerpi n, strongly enhance the accumulation of the test substrate of MXR, rho damine B, in the gills of the mussel Dreissena polymorpha, used as a m odel system for testing MXR-inhibiting potential. (C) 1998 Elsevier Sc ience B.V. All rights reserved.