Arsenic Metabolism in Terrestrial Oligochaetes and Marine Polychaetes

Arsenic is probably best known for the toxic properties of some of its compounds. However the bioavailability and toxicity of As is highly dependent on its chemical form varying from highly toxic inorganic to less toxic or harmless organoarsenic forms. Organoarsenic species are common in marine organisms where they are thought to represent metabolic end products of a process for detoxifying inorganic As. While arsenoriboses representing important compounds in the process of detoxification predominate in marine algae and animals feeding on them, they have been surprisingly identified in terrestrial organisms. For the first time, a study of the applicant has shown the presence of these compounds and two unknown compounds in extracts of earthworms from Styrian agricultural soils rich in inorganic As. The pathway of remarkably toxic arsenate in soil to harmless arsenosugars in living organisms is of toxicological importance and calls for further investigation especially with respect to elucidate the origin of such compounds. Therefore the supposed project "As metabolism in terrestrial oligochaetes and marine polychaetes" at Odense Fjord has the aim to clarify these transformations. Because marine organisms generally contain higher As concentrations than terrestrial ones, the higher As concentrations expected in marine worms from the same phylum should help studies on arsenic metabolism. The results will be linked to Styrian earthworms. Investigations should point out the natural variability for As and its tissue distribution in worms. Furthermore it is planned to determine the different As species with special emphasize on arsenosugars. Besides determining the As compounds in polychaetes and oligochaetes from natural systems, the uptake and biotransformation of As by those animals under defined conditions will also be investigated. Moreover, a mass balance should be carried out. And finally, the possible role of microorganisms in the worm or soil in the observed As biotransformations will be part of the research program.