We developed a method to determine tissue-specific distribution of trace metals in Daphnia magna by means of synchrotron-based micro-X-ray-fluorescence analysis (SR-XRF). This technique allows determining high-resolution 2-D elemental integration maps as well as tomographically obtained element sections through certain regions of interest. Complementary high resolution CCD camera images of tissue structure allow for element-to-tissue correlation. Investigation of several types of sample preparation showed that dehydration through an acetone-water series followed by drying in hexamethyldisilazane gave the best sample for subsequent analyses. Next, we determined the elemental distribution of Ca, Zn, Fe, and K in non-exposed daphnids. This confirmed the very distinct accumulation of Ca in the exoskeleton. Also, all elements were well represented in osmoregulatory tissue. Zn also exhibited a marked accumulation in gut tissue and in developing embryos. Daphnids exposed to 120μg Zn/L exhibited a clear increase of Zn accumulation in the osmoregulatory tissue. The techniques presented form a promising analytical tool to investigate tissue- specific accumulation of trace elements and its link with mechanisms of toxicity.
K. A. C. De Schamphelaere L. Vincze C. R. Janssen B. De Samber R. Evens G. Silversmit T. Schoonjans F. Vanhaecke I. Szaloki G. Falkenberg D. Adriaens
Laboratory of Environmental Toxicology and Aquatic Ecology, Ghent University (UGent), Jozef Plateaus Department of Analytical Chemistry, Ghent University (UGent), Krijgslaan 281, B-9000 Gent, Belgium Institute of Experimental Physics, University of Debrecen, 4026 Debrecen, Bern t r 18/a, Hungary Hamburger Synchrotronstrahlungslabor at DESY, Notkestr. 85, D-22603 Hamburg, Germany Evolutionary Morphology of Vertebrates and Zoology Museum, Ghent University (UGent), K. L. Ledeganck