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Many marine organisms inherently express the presence and function of a new defence mechanism, termed multixenobiotic resistance mechanism (MXRM) because of its similarity to multidrug resistance (MDR) found in tumor cell lines resistant to chemotherapeutic drugs. However, previously no information was available on a possible induction of the activity of MXRM in organisms living at polluted sites. The purpose of the present study was to demonstrate the inducibility of this defence mechanism in the marine snail Monodonta turbinata, an organism known to inhabit a wide range of environmental conditions existing along a pollution gradient. Specimens of M. turbinata used in the present study were collected from March 1993 through March 1994 near Rovinj, Croatia. The accumulation of generally labelled 3H-vincristine (3H-VCR) in the gills of snails living at an unpolluted site was 67% higher and very sensitive to verapamil, an inhibitor of P-glycoprotein activity in comparison to snails living at a polluted site. The accumulation of vincristine (VCR) in snails from a polluted site was reduced and insensitive to verapamil due to the induced state of P-glycoprotein, as was demonstrated immunochemically by the enhanced concentration of a 140 kDa protein cross-reacting with the polyclonal antibodies raised against mammalian P-glycoprotein. MXRM could be induced in snails from the unpolluted site to the level found in snails living at a polluted site either by transplantation for 3 d to a polluted site, or by exposure for 3 d to sea water polluted with Diesel-2 oil (hydrocarbon concentration equivalent to 50 ppb of Kuwait oil). Discovery of the inducibility of this new defence mechanism in aquatic organisms may have important implications in ecotoxicology, as was demonstrated by a 104% enhanced accumulation of VCR in the presence of the MXRM-inhibitor, the so-called “chemosensitizer”. Besides, a striking difference in the levels of MXRM-elements (the sensitivity of the accumulation rate of xenobiotics to verapamil, immunochemical expression of P-glycoprotein, and the sensitivity of the binding of xenobiotics on membrane vesicles to verapamil) found between specimens living at the polluted and unpolluted sites offers a new molecular biomarker for exposure to pollutants.

The trochid snail Monodonta turbinata was exposed to various concentrations of mercury and cadmium salts at different temperatures. Survival was significantly affected by salt concentration and by temperature, as well as by the interaction between them, so that the toxicities of both mercury and cadmium salts were found to be enhanced at higher temperatures. The ecological significance of these results on this Mediterranean littoral trochid is discussed.

The effects of zinc and copper pollution on the allozymic variation of phosphoglucose isomerase (Pgi) genotypes were tested in the Mediterranean marine gastropods Monodonta turbinata and M. turbiformis in 26 laboratory tests involving 2 081 adult individuals, with 545 survivors. Our results indicate differential survivorship of electrophoretical Pgi allozyme genotypes for both pollutants. Zinc pollution selected against the allozyme genotype SS in M. turbinata, whereas no differential survivorship was observed in M. turbiformis which lacks this allozyme. Copper pollution selected against the MM genotype in both species. These results are inconsistent with the neutral theory of allozyme polymorphisms and appear to reflect the adaptive nature of some Pgi genotypes in these marine gastropods.

1. 1. The green pigment in the foot of Monodonta turbinata was isolated. 2. 2. The free pigment was found to be a hydrophilic substance green in acid and yellow in alkaline solution. 3. 3. The absorption spectrum of the pigment in methanolic HCl showed maxima at 680 and 370 mμ (E370/E680=0.87), and inflexions at 440, 330 and 270 mμ. The zinc complex exhibited an absorption maximum at 665–670 mνm, and in inflexion at 615 mμ, after oxidation with iodine. 4. 4. The pigment gave the Gmelin reaction. It did not react with diazotised sulphanilic acid. 5. 5. It is suggested that the pigment is a bilatriene. 6. 6. Green pigment with an identical absorption spectrum was isolated from foot tissue of the realted species Monodonta articulata.

1. 1. A blue-green pigment has been isolated from shells of the trochid Monodonta turbinata . 2. 2. The pigment behaved as a highly polar compound and gave the Gmelin reaction. 3. 3. The absorption spectrum of the pigment in methanolic HCl showed maxima at 630, 363 and 315 mμ and inflexions at 405 and 270 mμ. The zinc complex of the pigment exhibited yellow-green fluorescence in u.v. light. On oxidation with iodine it showed a shoulder at 660 mμ extending to 610 mμ in the absorption spectrum. 4. 4. It is suggested that the pigment is a biladiene probably related to the bilatriene present in the foot of M. turbinata .