Effects of TBT on coelomocytes of the marine worm Sipunculus nudus

Tributyltin (TBT) has been widely used as effective biocide in antifouling paint formulations. As a consequence, TBT was introduced into the aquatic environments, where it shows a variable persistence in water column, depending on the environmental conditions. In sediments, TBT is more persistent, with a half-life from few months to several years. Moreover, as this compound is highly lipophilic, contaminated sediments represent a risk for benthic organisms which can accumulate it. In the present study, we investigated the effects of various concentrations of TBT on some functional responses of short-term cultures of coelomocytes from the marine worm Sipunculus nudus, a sediment-feeding sipunculan common in the littoral zone of the North Adriatic Sea (Italy), in order to evaluate the possibility to use these animals as sentinel organism in biomonitoring studies. At the end of the treatments, the viability of coelomocytes, as monitored by Trypan Blue dye exclusion test, was 70% at 10 μM TBT, so that used concentrations (0.01 to 1 μM) were considered to be sublethal. At 10 μM TBT, cytolysis of haemerythrocytes was also observed. In the presence of TBT, the amoebocytic index, i.e., the percentage of coelomocytes with amoeboid shape, and the endocytotic index, i.e., the percentage of coelomocytes containing Neutral Red dye, were signifi cantly (p < 0.001) inhibited at 1 μM. Lysosomal activity index, i.e., lysozyme activity measured spectrophotometrically on coelomocytic lysate, was reduced at 0.05 μM (p < 0.05) and 0.1 μM (p < 0.01). The apoptotic index, i.e., the percentage of coelomocytes with chromatin condensation detected with Acridine Orange, showed a signifi cant (p < 0.001) increase at 1 μM after 1 h. All these indexes can be proposed as biomarkers being sensitive, rapid and reproducible and can be considered as useful tools for monitoring TBT contamination in marine sediments.