Oxygen isotope composition of living land snail shells: Data from Italy

Sixty-seven shells of living land snails were selected from 31 different localities across Italy to investigate the relationships between their oxygen isotopic composition (δ18Os) and the mean value of local rainfall (δ18Op). Despite the difficulty for some localities to correctly estimate the oxygen isotopic composition of local rainfall, a good relationship was found. This indicates that the oxygen isotopic composition of environmental water used by the snails is, in Italy, strictly related to that of the local meteoric precipitation. However, the relationship found is substantially different from that previous established for central Europe, indicating that regional climatic conditions are important in defining the final isotopic composition of land snail shells. Moreover, these equations may not hold for different climatic conditions existing during, for instance, glacial and interglacial periods. The data also show that isotopic differences among species are relatively narrow and that they may depend on ecological factors (i.e., style of life) rather than any clearly identifiable different vital offset.