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Accumulation of Cd, Co, Cr, Cu, Fe, Mn, Ni and Zn was studied in the sediments, Cymodocea nodosa leaves, roots and stems and in two gastropods from an area adjacent to a ferro-nickel smelting plant and a control site on the east coast of Greece. In the sediment, the metals, with the exception of Cu, have significantly higher concentrations in the polluted than in the clean site. There is a tendency for C. nodosa tissues in the polluted area to have higher concentrations of metals although the differences are not always statistically significant. Co, Mn, Ni and Zn are in higher concentrations in the leaves than in the other tissues, a trend more obvious in the polluted site. Concentrations of metals in the viscera of the gastropods Cerithium vulgatum and Monodonta mutabilis are higher than in the muscle (except for Cd) and significantly higher in the animals from the polluted site. It is suggested that Mn is taken up from the water by C. nodosa leaves, which in the form of detritus enter C. vulgatum. Mn concentrates in the viscera of C. vulgatum in the form of granules. Zn follows the same route with additional amounts being taken by C. vulgatum directly from the water. © 1998 Elsevier Science Ltd. All rights reserved

Marine snails excrete metals via the gut. The sediment-feeding, tower shell Cerithium vulgatum, from a polluted environment, accumulates Cr and Ni to 3500 ppm dry weight in the faecal pellets. Pellets from C. vulgatum and the grazing, top shell Monodonta mutabilis were incubated in surface and deeper anoxic layers of clean and metal-polluted sediment. Pellets retained the original load of metals and in some cases gained Ti, Cr, Mn, Fe and Ni. Effects were modified by sediment properties. Pellets of C. vulgatum are durable, membrane-bound structures and they reduce metal bioavailability to food chains by compartmentalization. Intracellular, phosphate granules bind metals in digestive glands of snails and they are excreted via the gut and faecal pellets. These granules were extracted from digestive glands of both species of snail and incubated in the same sediments. Magnesium phosphate granules from M. mutabilis dissolved but calcium/metal phosphate granules from C. vulgatum remained; they had differentially retained or lost Mn, Fe, Co, Ni and Zn according to the type of sediment.

In any polluted marine environment, different invertebrate species contain markedly different concentrations of heavy metals. Primary producers take metals from seawater, but animals take additional metals from diets of animals, plants and detritus. Metals in a dietary organism of a food chain have varying reactivities and they follow different biochemical pathways. Excess metals are bound by ligands to form insoluble compounds within cytological compartments. These metabolic systems prevent the disruption of normal biochemical reactions by metals. The present work on Mediterranean invertebrates, initiated in Greece in 1993, used digestive glands from three species of marine snail,Monodonta mutabilis (Philippi),Cerithium vulgatum (Bruguiere), andMurex trunculus (Linnaeus) as prey tissue, and hermit crabsClibanarius erythropus (Latreille) as predators; the digestive glands and faecal pellets from all animals were analysed by atomic absorption spectroscopy and x-ray microanalysis. Most metals detoxified by the snails are unavailable to the crabs and they pass straight through the gut and appear in the faecal pellets. This applies to significant proportions of the manganese, nickel, copper, zinc and silver which are bound electrostatically to phosphate or covalently to sulphur within membrane-bound intracellular compartments. Cadmium and chromium are transferred to the crabs. In digestive glands of snails, cadmium is bound to soluble highsulphur protein in the cytosol; the cytology of chromium in these animals is not known.

LT50 values obtained for Monodontaturbinata exposed to heavy metal ions were as follows: 25.2 days after exposure to final concentration of 1.0ppm Cd+2; 21.2 days for 0.1ppm Hg+2; 25.2 for 0. 5ppm Cr+3 and 16.8 days for 0.5ppm Cr+6, compared to 32.8 days for the control. The final concentrations of metal ions in the mollusc tissue increased by 20 times in the Hg+2, and by 10 times in the Cd+2 treated Monodonta, compared to the untreated control. The normal contents of cytochromes be and P450 in Monodontaturbinata digestive gland microsomes were 195±51 and 58±20 nmol/mg protein, respectively. NADPH-cytochrome c reductase activity was 5.9±3.0 nmol/min/mg protein. Exposure to all heavy metal ions had a destructive effect on the two hemoproteins, especially on cytochrome P450, and a pronounced impact on NADPH-cytochrome c activity which was reduced to about 50% in the treated mollusc. No alarming concentrations of metal ions could be detected in Monodontaturbinata collected from different sites along Israel Mediterranean coast.

The effects of copper and chromium are studied on the cosmopolite marine prosobranch Monodonta turbinata (Born). The influence of Cu and of the mixture Cu + Cr was tested by the determination of the LC50 (48 h), the LT50, the respiration and bioaccumulation rates. The tested concentrations of metals caused a significant reduction of the respiration rate of Monodonta. Cu accumulates progressively in the tissues of the prosobranch proportionally to the Cu concentrations of the tested media. In all experiments [LX50 (48 h), LT50, oxygen consumption and bioaccumulation] when Cu and Cr act jointly, an antagonism is observed: the mixtures caused less pronounced effects than Cu and Cr acting alone. Generally Monodonta was found to be much more sensitive to Cu than other benthic species.

Cadmium, Co, Cr, Cu, Fe, Mn, Ni, and Zn were measured by atomic absorption spectroscopy in the digestive gland of the marine gastropods Cerithium vulgatum, Monodonta spp., Murex trunculus, Conus mediterraneus , and Patella coerulea , sampled during different seasons at four sites near a ferro-nickel smelting plant and two control sites on the east coast of Greece. Near the smelter there were higher concentrations of all metals in Cerithium (except Cu) and Murex , and of Ni and Co in Monodonta , compared with the control sites, which indicated that the plant contaminated the environment. The animals from the contaminated area showed marked differences in concentrations which were associated both with the genera and the sites, while there were no consistent seasonal variations.

Strontium concentrations have been determined in the outermost portions of shells of Patella coerulea, Monodonta articulata and M. turbinata. The incorporation of Sr into the carbonate seems to be influenced by the rate of growth of shells and by environmental temperatures, besides the Sr/Ca ratio in seawater. Temperature and growth rate may act either alternatively or concurrently; the latter is the case for Patella in the whole annual cycle, and for both Monodonta species during the higher temperature interval (18°–25°C). In the lower temperature interval (13°–17°C), the polymorphic composition of M. articulata shells exerts a primary control on Sr contents, whereas in M. turbinata the ratio Sr/Ca seems to be controlled by environmental temperatures, in a thermodynamic sense.

Magnesium, temperature and rate of growth interrelations are studied in the shell material of three gastropod species: Patella coerulea, Monodonta turbinata and M. articulata . Mg and temperature are correlated positively in the shell calcite of Patella coerulea and Monodonta articulata , and negatively in the aragonite of M. turbinata shells. The correlations are often statistically significant at a high level of confidence and can be used as tools for ecological and paleoecological investigations. Temperature seems to be the main causal factor that controls Mg incorporation into the shell calcite, whereas, in the aragonitic M. turbinata shells, the rate of growth appears to play a determinant role on Mg concentrations.

The oxygen consumption of inactive animals of four species of Mediterranean trochid was measured in air and sea water at temperatures commonly recorded on the shore. The loss of mantle cavity fluid significantly lowered the aerial oxygen consumption of all four species. The aquatic oxygen consumption of the four species after 12 h settlement in the respirometer was not significantly different from that measured after 1 h. The high-shore Monodonta lurbinata (Born) and M. articulata (Lamarck) experience a maximum of 60 to 70% aerial exposure, wide temperature fluctuations, and can maintain an aerial rate of oxygen consumption similar to the aquatic rate. They have temperature dependent rates of oxygen consumption with similar Q 10 values in both air and water between 20 and 30°C. The low-shore Gibbula richardi (Dayraudeau) and G. rarilineata (Michaud) are characterized by a low maximum percentage aerial exposure, a more stable thermal environment, an aerial rate of oxygen consumption lower than the aquatic rate, temperature dependent respiration rates between 20 and 30°C in sea water but a temperature coefficient not significantly different from 1 in air. These patterns of oxygen consumption are reflected in the 50% survival times of the trochids in air at 25°C. The pattern of respiration in air and water of a wide range of intertidal gastropods has been related to the maximum percentage aerial exposure experienced on the shore.

The trochid snail Monodonta articulata Lamarck was exposed to mercuric sulphate at concentrations of 0.2, 0.5, 0.8 and 1 ppm Hg++. At 24 h, retraction into the shell was observed in 0.8 and 1 ppm Hg++; this retraction increased in these concentrations at 36 h. Retracted snails died if retained in the solutions, but generally recovered within 24 to 48 h if transferred to uncontaminated sea water. Immersionemersion behaviour and interface activity were studied over 24 h by means of an aktograph; snails in normal sea water spent more time below than above the water surface, and exhibited frequent periods of activity. Exposure to mercuric sulphate at concentration of 0.25, 0.5, 0.8 and 1 ppm Hg++ progressively reduced both the length and frequency of activity periods. From 0.5 ppm Hg++ upwards, emersion periods increased, and immersion periods decreased. Oxygen consumption of snails was measured in sea water and in mercuric sulphate at concentrations of 0.2, 0.5, 0.8 and 1 ppm Hg++. Oxygen consumption decreased significantly with each progressive rise in mercury concentration. It is considered that mercury affects M. articulata by interfering with respiration, initially reducing interface activity, then forcing the snail for longer and longer periods out of the water. Retraction occurs when activity is no longer possible. It is concluded that respiratory and behavioural alterations of this nature would afford a good indicator of the presence of sub-lethal concentrations of pollutants.

In the digestive glands of gastropod molluscs, metals are metabolized in the sense that they are subject to inorganic biochemical processes within the epithelial cells and lumen of the digestive tubules and the pore cells in the intervening connective tissue. These systems have been examined in the tower shell Cerithium vulgatum Bruguieres, a sediment feeder, the top shell Monodonta articulata Lam., a grazing herbivore, and in the whelk Murex trunculus L., a carnivore whose prey includes Cerithium . These animals were taken from a Mediterranean environment polluted by heavy metals. In all three species the metals are compartmentalized within mineralized granules as phosphates and within lysosomal residual bodies in association with sulphur. However, the extent to which a particular metal is accumulated and the relative proportions that are bound within the different compartments are factors that are primarily determined by the species and not the concentration available in the environment. Thus Cerithium accumulates high concentrations of a wide range of metals from the ingested sediment and these are rendered insoluble and non-toxic in the digestive gland. This unavailability is transferred to Murex when it eats Cerithium because Murex does not accumulate the full range of metals from its prey. Indeed, for some metals there appears to be bioreduction rather than bioamplification. The grazing herbivore Monodonta articulata accumulates a third distinct spectrum of metals. The accumulations in each species do not reflect the levels of all the metals in the environment. The presence of metals in the digestive glands is associated with the removal of magnesium from the phosphate granules but also with an increase in the concentration of magnesium in the tissue. It is proposed that metals induce the formation of magnesium phosphate as a source of metal-binding phosphate ions.

Shells of the mollusks Cerastoderma (Cerastoderma) edule (Linnaeus 1758) and Monodonta (Osilinus) articulata Lamark 1822 from salt evaporate basins in western Sicily are studied and the effect of environmental conditions (particularly salinity and water chemistry) on mineralogy and chemical composition is investigated and discussed. The elements determined both in seawater and shell carbonate are: Ca, Mg, Mn, Fe, Ni, Co, Cu, Zn, Sr and Pb. Both species studied discriminate against all the minor and trace elements determined; the degree of such discrimination, for some elements, is inversely related to salinity. The mineralogical composition of the shells ( Monodonta has a mixed mineralogy while Cerastoderma is entirely aragonitic) appears to be controlled neither by temperature nor by salinity. In Monodonta shells direct correlations have been found between the following parameters: calcite-Sr (in younger shells only), calcite-Fe, calcite-Pb (in older shells only), calcite-Zn, salinity-Mg and salinity-Pb, whereas inverse correlations were observed between calcite and Sr (in older shells only) and calcite and Pb (in younger shells only). In Cerastoderma shells a direct correlation was found between salinity and Fe and Mg. The thickness of the shells appears, in both species, to be an inverse linear function of salinity.

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.

Five species of marine gastropods (Monodonta turbinata, M. turbiformis, Cerithium scabridum, Littorina punctata and L. neritoides) were exposed to cadmium in the laboratory. The enzyme phosphoglucose isomerase (PGI) tested electrophoretically showed for all five species a statistically significant higher proportion of heterozygotes among the dead animals than among the survivors in the range of concentration tested. This pattern seems to have been established by natural selection. Further, it could be used in developing biological monitors of present and past cadmium pollution based on the genetic response of natural populations to this specific pollutant.

1. 1. Lactate dehydrogenase activities in extracts of a gastropod, Monodonta sagittifera, and a sea urchin, Arbacia lixula, were determined by change in light absorbance of a dye mixture on addition of salts of lactic acid in each isomeric form. 2. 2. The Monodonta extract catalyzed the oxidation of d -lactate only, with an apparent Michaelis constant of 180 mM. 3. 3. Weight-specific enzyme activity of Monodonta was proportional to the −0·18 power of total body weight. 4. 4. The sea urchin appeared to contain two enzymes of equal activity, one specific for l -lactate and one specific for d -lactate.

The species Monodonta (Osilinus) articulata Lamark 1822 is recorded as having a shell with mixed minerals: a calcitic microstructural unit is comprised between 2 aragonitic layers.