The planktonic foraminifera Orbulina universa is living in the photic zone of marine water columns and it possesses photosynthetic microalgae symbionts in its cytoplasm (dinoflagellates). The transfer of carbon compounds from the symbiotic microalgae to the foraminifer host cell is a continuous process. During day microalgae might migrate on the spines to start to transfer carbon compounds from their starch vesicles to the lipid droplets of the foraminifer. During night, nearly the total amount of photoassimilates accumulated during the light phase is transferred from the symbiont starch vesicles to the host lipid droplets.