A BioBank for mussels and clams of the Adriatic Sea: an integrated biological approach to support farming management

This thesis studies the temporal dynamics of health status of Mediterranean mussels (Mytilus galloprovincialis) and striped Venus clams (Chamelea gallina) in productive sites along the Emilia-Romagna coastline (Northwestern Adriatic Sea), identifying early indicators of physiological impairments caused by climatic events or chemical pollution that can reduce bivalve productivity. Field samplings over multiple years, seasons, and locations provided a comprehensive dataset of biometric parameters, physiological indices, and transcriptional profiles of genes underpinning bivalve core physiological processes (i.e., metabolism, stress response, shell biomineralization). Results showed that local conditions may shape the resilience of C. gallina to environmental changes, with responses to the 2022 heatwave varying by site productivity. Low-productivity sites clams increased feeding and digestive gene activity, while high-productivity sites clams exhibited healthier metabolism and enhanced antioxidant and immune responses. Analysis of stability and expression of six housekeeping gene transcripts commonly used as reference genes in qPCR analyses with mussels identified ribosomal RNA genes as the most stable under field conditions. Expressions of the most variable transcripts actin and elongation factor-1α significantly correlated with seasonal/latitudinal changes of abiotic parameters and physiological indices, leading to consider their expression profiles as molecular biomarkers of mussel general physiological status. Mussels investigated during the 2022 heatwave showed changes in metabolic and detoxification/cytoprotective transcripts, underscoring the physiological accommodations to cope with harsh environmental conditions, while maintaining biomineralization and shell growth. A field study on mussel bioaccumulation of pharmaceuticals and pesticides showed that the seasonal accumulation up-regulated metabolic gene products but down-regulated detoxification and lysosomal related transcripts, suggesting an energy shift towards coping with pollutants. Additionally, the digestive gland microbiome harbored adaptable xenobiotic-degrading genes, likely mitigating xenobiotic host exposure. Overall, this research attempts to understand how bivalve physiology is influenced by complex environmental interactions, supporting the development of climate-adaptive strategies for sustainable bivalve production in the Adriatic region.