Carbon and oxygen isotope variations within the shell of an African land snail (Limicolaria kambeul chudeauiGermain): a high-resolution record of climate seasonality?

Stable isotope analyses at high-resolution intervals along the growth axis of a shell of the land snail Limicolaria kambeul chudeaui Germain, collected in Ethiopia, show a cyclic pattern of d 18 O variation. The cycles have regular periodicity but vary in amplitude. The shape and amplitude of the shell d 18 O cycles is consistent with seasonal changes in the amount and isotopic composition of the rainfall, coupled with tempera ture and evaporative effects. The number of cycles (10) corresponds to the estimated lifespan of Limicolaria. Generally constant d 13 C values suggest unvarying diet, environmental CO 2 influences, and metabolism throughout the snail's life, except for one interval of large variations in both d 13 C and d 18 O that may be related to the onset of reproductive activity. If similar results can be obtained for fossil shells, they may provide a high-resolution record of past seasonal climate variability.