Combined effects of temperature, salinity and pH on immuneparameters in the clam Chamelea gallina

The role of haemocytes in immune responses in bivalves is widely demonstrated. Immunosuppression due to stressful environmental conditions can strongly affect survival and growth of marine bivalves. In a global climate change scenario, the evaluation of possible effects of variations in environmental parameters on immune responses of bivalves deserves particular attention. In this context, adults of the clam Chamelea gallina were used to investigate the cumulative effects of pH, temperature, and salinity on clam haemocyte parameters [total haemocyte count (THC), endocytotic activity, and haemolymph lysozyme activity]. An experimental flow-through system was setup to test simultaneously effects of different temperatures (22 and 28 °C) and pH (8.1, 7.7, and 7.4). Three experiments were performed at 28, 34, 40 psu salinity, and immune parameters of clams were measured after 7 days exposure. At 28 psu, THC decreased markedly with increasing temperature at each pH values. Endocytotic activity increased with increasing temperature and decreasing pH. At 34 psu, THC increased with increasing temperature and decreasing pH, except at 7.4 pH. Endocytotic activity showed the highest values at7.7 pH and 28 °C, and 7.4 pH and 22 °C. At 40 psu, both THC and endocytotic activity decreased markedly with increasing temperature and decreasing pH. Overall, results obtained demonstrated that both immunomarkers allow to highlight stress conditions in clams, and indicate differing immunomodulation patterns, on the basis of the experimental conditions tested at least. Acknowledgements: This work was funded by the Italian Ministry for Environment, Land and Sea (IMELS) in the frame of the CIRCLEMED Project “The integrated impacts of marine acidification, temperature and precipitation changes on bivalve coastal biodiversity and fisheries: how to adapt (ACIDBIV)”.