IMMUNOTOXICITY OF CU(I) AND IRGAROL 1051 IN ASCIDIANS

After the widespread ban of TBT due to a severe impact to coastal biocenoses mainly related to its immunosuppressive effects on both invertebrates and vertebrates, alternative biocides like Cu(I) salts and the triazine Irgarol 1051 (previously used in agriculture as a herbicide) have been massively introduced in combined formulations of antifouling paints against a wide spectrum of fouling organisms. Our interest in the study of ascidian defense reactions led us to investigate the effects of Cu(I) and Irgarol on cultured phagocytes of the colonial ascidian Botryllus schlosseri, as previously done with TBT. We set up short-term hemocyte cultures (60 min) exposed to sublethal concentrations of these compounds (Cu(I) LC50 = 281 µM; Irgarol LC50 > 500 µM). In contrast to TBT, both substances did not cause significant effects on cell morphology. Generally, Cu(I) appeared more toxic than Irgarol: it significantly inhibited (p < 0.05) yeast phagocytosis at 0.1 µM, and affected calcum homeostasis and mitochondrial cytochrome-c-oxidase activity at 0.01 µM. Both substances were able to change membrane permeability, induce apoptosis for concentrations of 0.1 µM and 200 µM for Cu(I) and Irgarol, respectively, and alter (with different mechanisms) the activity of hydrolases (acid phosphatase, esterases) and oxidases (phenoloxidase). Although both the xenobiotics are less toxic than TBT and their LC50 values are lower than the concentrations in the aquatic environment, their impact on organsms must be considered as they can alter immune defences and consequently endanger the survival of the individual.