EFFECTS OF SUBLETHAL CONCENTRATIONS OF TRIPHENYLTINACETATE ON RAINBOW-TROUT (ONCORHYNCHUS-MYKISS)

To evaluate the toxic effects of sublethal concentrations of the fungi cide triphenyltinacetate (TPTAc), a prolonged toxicity study was made on rainbow trout (Oncorhynchus mykiss). Fish were exposed to TPTAc con centrations ranging from 1 to 6 mu g TPTAc/L for 28 and 18 days, respe ctively, using a flow-through exposure system. Hematological findings included an increase of the total number of erythrocytes and an elevat ed incidence of erythrocyte degradation stages at 4 mu g TPTAc/L and h igher. 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 i ncreased in fish exposed to 1 mu g TPTAc/L, the number of leucocytes t ended to decrease at higher concentrations. The percentage of lymphocy tes within the differential blood cell count decreased. The histopatho logical examination of TPTAc-exposed fish showed a dose-related lympho cytic depletion of the spleen, accompanied by a proliferation of retic uloendothelial cells and an increased erythrophagia even at the lowest TPTAc concentration. In severe cases, cell necrosis was evident. In l iver tissue, a depletion of the glycogen deposits within the hepatocyt es could be detected in fish exposed to 4 and 6 mu g TPTAc/L. The anal ysis of the phenyltin compounds within various organs of fish by HRGC- FPD revealed remarkable concentrations of triphenyltin of up to 16.1 m u g/g with the following order of residue levels: liver > kidney > spl een > 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 b e present in aquatic environments.