Russo, Tania (2024) Mytilus galloprovincialis as a model to approach ecotoxicological aspects of marine biological invasions. [Tesi di dottorato]

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Abstract

Background In this study, crucial ecotoxicological issues have been approached by using the molluscan bivalve species Mytilus galloprovincialis as a model organism. A special focus has been placed on the Mediterranean Sea, which is one of the major biodiversity hotspots under threat in the world, negatively impacted by both biological invasions and anthropogenic pollution. In addition to the negative and far-reaching impacts of invasive marine species per se, a growing literature is raising major concerns about the effects of bioactive substances carried by allochthonous species in the colonized environments, also because their ecotoxicological potential often adds to that of anthropogenic hazardous compounds widespread in marine ecosystems. Among the bioactive metabolites from exotic species, major attention has been paid in this study to the alkaloid caulerpin from green algae of the genus Caulerpa, since this compound already showed a panel of biological properties suggesting a non-negligible impact on native fauna. Given the similarities in the mechanism of action of caulerpin with that of fibrate drugs, the action of caulerpin has been compared to that of fenofibrate which is widely considered dangerous for aquatic fauna. On the other hand, since caulerpin co-occurs in the marine environment with caffeine, which is an anthropogenic pollutant widely recognized as a hazard to marine animals, the possible synergistic effects of caffeine and caulerpin have been also evaluated. A further aspect of this study concerned the invasive calcareous sponge Paraleucilla magna, which colonizes mussels’ farms in the Mediterranean. Although little is known about the sponge’s chemical composition, the toxicological potential of its crude extracts has been tested. Methodology and Principal Findings The above issues have been approached by proposing via food pure metabolites and crude extracts to mussels, followed by biochemical analyses, NMR-based metabolomics, and histopathological examinations. Results obtained indicated that caulerpin did not affect mussel physiology, while several impacts were observed after the exposure to fenofibrate (Chapter 2). Also, no cumulative effects were observed when mussels were exposed simultaneously to caulerpin and caffeine (Chapter 3). Finally, the study on P. magna (Chapter 4) clarified that the sponge’s acetone extract did not affect mussels, while the diethyl ether and butanol extracts induced significant variations in osmolyte levels and biochemical markers. Significance Overall, the present study confirms the harmful effects of both fenofibrate and caffeine, underscoring the potential risks associated with their presence in the marine environment. The findings also support the safety profile of caulerpin, a metabolite derived from highly invasive marine species, paving the way for further investigation in support of its possible use for nutraceutical and aquaculture applications, and the sustainable exploitation of the huge biomass from invasive species. Finally, the study suggests that the invasive sponge P. magna may pose a real chemical threat to the Mediterranean Sea, although more comprehensive additional research to determine which specific sponge metabolites are responsible for the observed effects is needed.

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