Evaluation of tissue morphology and gene expression as biomarkers of pollution in mussel Mytilus galloprovincialis caging experiment

- The paper describes how marine pollution modifies the biology of aquatic species.
- Measurable parameters at different levels of biological organization are introduced.
- The evaluation of mRNA is widely used as a biomarker to highlight side effects.
- mRNA expression, even if transient, can anticipate morphological changes.
- mRNA is a useful endpoint for an integrated evaluation of marine ecosystem pollution.

The ecosystem is being anthropogenically disturbed, which has serious consequences for the environment and human health, having strong social and economic impacts on the community. One of the most common methods to evaluate the effects of toxic contaminants is based on biomonitoring, e.g., placing Mytilus galloprovincialis in the polluted areas investigated. In this study, we have combined two different methods, transcriptomic and morphological analysis, with the purpose of determining whether cell morphology and the ultrastructural organization of our animal model are related to gene expression in outdoor experiments. The most pronounced changes were observed in mussel gills and digestive gland for mRNA involved in protein machinery (18S, 28S and EF1), while HSP70, MT10, CYP4Y1, SOD1, and CAT mRNAs showed scattered modifications not related to the studied area. In agreement with 18S, 28S, and EF1 mRNA evaluation, optical and electron microscopy demonstrated an initial inflammatory response of the cells that can lead to apoptosis in the caged mussels in all the polluted areas. In conclusion, the application of a multi-disciplinary approach proved to be effective for assessing the biological effects of contaminations on the health of aquatic organisms, and thus suitable to be applied in eco-toxicological studies. Although affected by several uncontrolled environmental variables, the assessment of mRNA can represent a useful endpoint for an integrated estimation of the overall threats to the sea environment within a field research approach.