Seasonal variation of trace metal concentrations in the digestive gland of the Mediterranean mussel Mytilus galloprovincialis: Comparison between a polluted and a non-polluted site

Abstract

Seasonal changes in metal (Cu, Fe, Mn, Pb, and Zn) concentrations were observed in the digestive gland of the Mediterranean mussel, Mytilus galloprovincialis, from both a polluted and a non-polluted population. Digestive gland of mussels from the polluted site showed metal concentrations appreciably higher than in non-polluted organisms, especially for Pb (up to 160 micrograms/g d.w.), Mn (up to 300 micrograms/g d.w.), and Fe (up to 8,500 micrograms/g d.w.), whereas the two populations showed maximum mean values, respectively, of 34 and 20 micrograms/g d.w. for Cu and 170 and 120 micrograms/g d.w. for Zn. Over 1 year (1991), differences between maximum and minimum values were moderate only in the unpolluted organisms. During gametogenesis, while the metal concentrations (expressed as microgram/g dry weight) decreased in the digestive gland, the tissue burden (as microgram) in that organ remained nearly constant or increased slightly. The apparent decrease in metal concentrations was probably due to the penetration of gonadic tissues into the digestive gland during gametogenesis, which biologically diluted metal concentrations in mussels from both the polluted and unpolluted populations. The effect of mussel size on trace metal concentrations in the digestive gland was demonstrated during different stages of the reproductive cycle. Higher concentrations were found in smaller organisms; however, during the spawning period, due to the fact that this is not a synchronous process within a population, the organisms exhibit a high variability in digestive gland weight which can mask this relationship when digestive gland weight is used as a size-index and as a parameter of the trace metal digestive gland burden.

Is the digestive gland of Mytilus galloprovincialis a tissue of choice for estimating cadmium exposure by means of metallothioneins?

“…Temporal variation of digestive gland mass is under influence of food availability and reproductive cycle. Since gonadic tissue penetrates into the digestive gland (Regoli and Orlando, 1993), two tissues cannot be separated by dissection (Regoli and Orlando, 1994). Lower concentrations of trace metals in the gonadic tissues (George and Coombs, 1977;La Touche and Mix 1982;Lobel and Wright, 1982) cause "biological dilution" of trace metal concentrations in the digestive gland.…”

Characterization of the cytosolic distribution of priority pollutant metals and metalloids in the digestive gland cytosol of marine mussels: Seasonal and spatial variability

“…Besides physico-chemical properties of the seawater, other factors related with the reproductive stage of mussels could also affect metal concentrations in the digestive gland (Regoli and Orlando 1994, Raspor et al, 2004, Ivanković et al, 2005. Therefore, the general trend of higher concentrations of cytosolic metals in March than in August as it was reported in this study for Cu, Cd and Zn (Table 3) could also be related with the possible influence of reproductive status.…”

“…In our knowledge cytosolic distribution of metals was not investigated with reference to seasonality. Yet, it is known that the level of total tissue and cytosolic metals show a seasonal variability dependent on the abiotic and biotic factors even when the environmental concentrations of metals remain unchanged (Regoli and Orlando 1994, Raspor et al, 2004, Ivanković et al, 2005. Similarly, it is found that biomarkers are also affected by seasonality (Ivanković et al, 2005; Bocchetti and Regoli , 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 5 organism.…”

Bioacumulação de metais pesados em moluscos bivalves: aspectos evolutivos e ecológicos a serem considerados para a biomonitoração de ambientes marinhos

“…No caso de estocagem, entende-se que o organismo faça um investimento metabólico para regular a concentração de alguns metais ("reguláveis"), conforme é a sua demanda metabólica de um dado elemento, e a sua biodisponibilidade no ambiente (Depledge & Rainbow, 1990). O zinco pode ser citado como exemplo de metal regulado por bivalves (Regoli & Orlando, 1994), o que dificulta avaliar a contaminação ambiental através dos dados de bioacumulação deste elemento em bivalves.…”