Integration of physiological, transcriptomic and metabolomic analyses reveals acute carbonate alkalinity stress responses in the gill of Asian clam (Corbicula fluminea)

Aquaculture is an effective approach to improve the utilization of saline-alkaline water. Corbicula fluminea is an important economically freshwater bivalve species in China, capable of adapting to certain levels of salinity and alkalinity. However, the mechanisms underlying its acute response to alkalinity remain unexplored. In this study, we investigated the effects of alkalinity (0, 10 and 20 mmol/L) on the gill tissue of C. fluminea (54 individuals, 22.18 ± 1.9 mm in shell length and 4.41 ± 0.66 g), employing integrated physiological, transcriptomic, and metabolomic analyses to elucidate its early responses. Histological and physiological results showed that alkalinity induced damage to gill tissue and significant physiological stress, evidenced by marked changes in indicators related to osmoregulation, oxidative stress, and immune response. Transcriptomic analysis identified many differentially expressed genes (DEGs) related to ion transport, oxidative stress, apoptosis, immune response, and metabolism. Metabolomic analysis revealed that differential metabolites (DMs) were predominantly lipids and lipid-like molecules. Integrated transcriptomic and metabolomic analysis revealed that both DMs and DEGs were enriched in pathways related to apoptosis, carbohydrate metabolism, and lipid metabolism. Overall, these results indicated the responses of C. fluminea to acute alkalinity stress involving in ion transport, apoptosis, immnue, and metabolism processes. These research results will accumulate data on the acute stress responses of freshwater bivalves to alkalinity, and provide a theoretical foundation for the saline-alkaline aquaculture of C. fluminea .