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(P877a) The subcellular distribution of Cd and Zn in brine shrimp: implications for trophic transfer.
Seebaugh, David*,1, Wallace, William1, 1 Center for Enviornmental Science, College of Staten Island, CUNY, Staten Island, New York, USA
ABSTRACT- Studies have shown that the trophic transfer of certain metals in aquatic systems may be controlled by the internal distribution within prey and that this distribution, and hence trophic transfer, may be influenced by detoxification mechanisms (i.e., metals bound to metallothioneins are more available to predators than metals associated with other cellular constituents). In the current investigation we examine the accumulation and subcellular distribution of Cd and Zn in the brine shrimp Artemia salina. Future studies will specifically focus on the trophic transfer of metal from A. salina to predators. Cultures of adult A. salina were exposed for 3 days to Cd (0, 0.1, 10 or 50 ppm) or Zn (0.58, 5.8 or 29ppm) through solution at a density of ~660 animals*l-1. 109Cd and 65Zn were used as radiotracers. Following exposure, animals were subjected to subcellular fractionation and tissue digestion procedures to obtain five operationally defined subcellular fractions (metallothioneins, "enzymes", organelles, metal-rich granules and cellular debris). A subcellular compartment containing Trophically-Available Metal (TAM) (metallothioneins, "enzymes" and organelles) was also constructed. Results show that due to the induction of Cd-binding metallothioneins, TAM-Cd increases from 57% to 80% over the range of exposure. Interestingly, while the proportion of Zn bound to metallothioneins decreases from ~50% to ~20% upon increasing Zn exposure, partitioning to organelles increases from ~10% to ~30%. This 'shifting' from the reliance on metallothioneins to organelles for the storage of Zn maintains a TAM-Zn of ~65%. Our prediction is that induction of Cd-binding metallothioneins in A. salina may result in a 'bioenhancement' of Cd trophic transfer, while no 'bioenhancement' of Zn would be expected.
Key words: subcellular distribution, trophic transfer, metallothioneins, metals
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