A synodic lunar reproductive cycle is demonstrated in Globigerinoides sacculifer. The reproductive cycles of Globigerinoides ruber and probably Globigerinella siphonifera are characterized by a semi-lunar periodicity. Inter-species differences in lifespan result in a different empty shell output. As a consequence, the sediment does not reflect the situation in the water column. Results yield consequences for the interpretation of sediment analyses and implications for paleoceanography. -from Authors