Immunotoxicity in ascidians: Antifouling compounds alternative to organotins III - The case of copper(I) and Irgarol 1051

After the widespread ban of TBT, due to its severe impact on coastal biocoenoses, mainly related to its immunosuppressive effects on both invertebrates and vertebrates, alternative biocides such as Cu(I) salts and the triazine Irgarol 1051, the latter previously used in agriculture as a herbicide, have been massively introduced in combined formulations for antifouling paints against a wide spectrum of fouling organisms. Using short-term (60 min) haemocyte cultures of the colonial ascidian Botryllus schlosseri exposed to various sublethal concentrations of copper(I) chloride (LC50 = 281 mu M, i.e., 17.8 mg Cu L-1) and Irgarol 1051 (LC50 > 500 mu M, i.e., >127 mg L-1), we evaluated their immunotoxic effects through a series of cytochemical assays previously used for organotin compounds. Both compounds can induce dose-dependent immunosuppression, acting on different cellular targets and altering many activities of immunocytes but, unlike TBT, did not have significant effects on cell morphology. Generally, Cu(I) appeared to be more toxic than Irgarol 1051: it significantly (p < 0.05) inhibited yeast phagocytosis at 0.1 mu M (similar to 10 mu g L-1), and affected calcium homeostasis and mitochondrial cytochrome-c oxidase activity at 0.01 mu M (similar to 1 mu g L-1) Both substances were able to change membrane permeability, induce apoptosis from concentrations of 0.1 mu M (similar to 10 mu g L-1) and 200 mu M (similar to 50 mg L-1) for Cu(I) and Irgarol 1051, respectively, and alter the activity of hydrolases. Both Cu(I) and Irgarol 1051 inhibited the activity of phenoloxidase, but did not show any interactive effect when co-present in the exposure medium, suggesting different mechanisms of action. (C) 2012 Elsevier Ltd. All rights reserved.