High‐Resolution Intrashell Oxygen Isotope Studies of Cathaica fasciola and Bradybaena ravida Land Snails and Their Environmental Implications

Abstract Intrashell oxygen isotope (δ 18 O s ) analyses of terrestrial snails have been carried out over two decades. However, the intraspecies/interspecies differences are not yet well understood. Here, we conducted a high‐resolution intrashell δ 18 O s study on 43 shells from Cathaica fasciola and Bradybaena ravida , and 1449 δ 18 O s data were obtained. These large amounts of data demonstrate the reproducibility of intrashell δ 18 O s . Our results suggest that C . fasciola and B . ravida have similar growing seasons mainly from March to October in the studied region. The ecological habits of the two species could explain the distinctive variations in their δ 18 O s sequences. Therefore, our study may interpret the discrepancy between the studies of land snail species and the stable/clumped isotopes of their shells. Moreover, the calculated average growth rate is ∼290 μm/day (from 250 to 330 μm/day) for nonadult C . fasciola . Thus, the use of snail shells for reconstructing high‐resolution terrestrial climate changes is promising.