Growth and shell properties variations in the clam Chamelea gallina along a latitudinal gradient of environmental parameters

Important ecological interactions between the organisms and their environment can be prompted by the studies along the latitudinal gradients, where it is possible to explore the varying environmental pressures on both biological and evolutionary processes. Thermal conditions vary with latitude and the ability to understand the relationship between growth and temperature is important because global climate change will be a thermal challenge to most ectotherms. Molluscs are particularly sensitive to different environmental parameters, showing macroscale shell morphology variations in response to environmental parameters. The aim of this thesis is to investigate variations in shell skeletal properties, mineral composition and growth along a latitudinal gradient (~400 km) in the Adriatic Sea (Italian cost) in relation to different environmental parameters. Shell morphology of the most irradiated and warmest populations was characterized by lighter, thinner, more porous and fragile shells, likely affecting the economic aspects of fisheries and the survival of the species. No variation was observed in shell CaCO3 polymorphism (100% aragonite), indicating no effect of the environmental parameters on the basic biomineralization processes. Moreover, C. gallina showed an increase in shell linear extension and net calcification rates towards South where warmer seawater, low fluctuations in salinity and high diversity of phytoplankton seem to be the most favourable environmental conditions for its growth. Because of the importance of C. gallina as commercial resource in the Adriatic Sea, variations in shell properties and in growth rates along the latitudinal gradient may have economic implications for fisheries and the observations from this research could help to guarantee the biological and economic sustainability of this resource.