Effects of sublethal concentrations of triphenyltinacetate on rainbow trout (Oncorhynchus mykiss)

To evaluate the toxic effects of sublethal concentrations of the fungicide triphenyltinacetate (TPTAc), a prolonged toxicity study was made on rainbow trout (Oncorhynchus mykiss). Fish were exposed to TPTAc concentrations ranging from 1 to 6 mu g TPTAc/L for 28 and 18 days, respectively, using a flow-through exposure system. Hematological findings included an increase of the total number of erythrocytes and an elevated incidence of erythrocyte degradation stages at 4 mu g TPTAc/L and higher. The hemoglobin content and the packed-cell volume increased as well at 4 and 1 mu g TPTAc/L. Whereas the total number of leucocytes increased in fish exposed to 1 mu g TPTAc/L, the number of leucocytes tended to decrease at higher concentrations. The percentage of lymphocytes within the differential blood cell count decreased. The histopathological examination of TPTAc-exposed fish showed a dose-related lymphocytic depletion of the spleen, accompanied by a proliferation of reticuloendothelial cells and an increased erythrophagia even at the lowest TPTAc concentration. In severe cases, cell necrosis was evident. In liver tissue, a depletion of the glycogen deposits within the hepatocytes could be detected in fish exposed to 4 and 6 mu g TPTAc/L. The analysis of the phenyltin compounds within various organs of fish by HRGC-FPD revealed remarkable concentrations of triphenyltin of up to 16.1 mu g/g with the following order of residue levels: liver > kidney > spleen > gills > muscle. Di- and monophenyltin were found only in traces of 1-109 ng/g in these organs. The present study indicates that TPTAc negatively affects rainbow trout in a concentration range that might be present in aquatic environments.