ORGANOPHOSPHATES IN THE ZEBRA MUSSEL DREISSENA-POLYMORPHA - SUBACUTE EXPOSURE, BODY BURDENS, AND ORGAN CONCENTRATIONS

Subacute exposures (10 d) of the freshwater mollusc Dreissena polymorp ha to disulfoton (10 mg/L), thiometon (6 mg/L), and its activated oxyg en analogue demeton-S-methyl (6 mg/L) corroborate earlier findings of organophosphate resistance and accumulation in the organism. Mortality occurred not before the ninth day of exposure. Mortality was induced at high ambient water concentrations and must be due to unknown specif ic organophosphate effects. Body burdens reached saturation levels wit hin one week being around 10 mg/kg wet weight for thiometon and 60 mg/ kg for disulfoton. Mussels dying during the tests showed lower tissue concentrations. Elimination of accumulated organophosphates was so low in the mussel, that an efficient metabolism of these compounds in the mussel was unlikely. Different organs of Dreissena previously acutely exposed (96 h) to the organophosphate thiometon (6, 12, 25, 50 mg/L) were analysed for their thiometon content. Thiometon could be found in all organs, but were highest in the anterior part of the viscera (230 mg/kg), where it was accumulated either in the digestive gland and/or in the gonadal tissue.