Neorhabdocoela oocytes - Palaeoecological indicators found in pollen preparations from Holocene freshwater lake sediments

Oocytes produced by aquatic flatworms of the order Neorhabdocoela are not destroyed by the chemical treatment of freshwater lake sediments for pollen analytical purposes. Until now these oocytes have commonly been ignored by palynologists. We present here the first detailed study of Neorhabdocoela oocytes from Central Europe, and discuss their palaeoecological significance. By analysing pollen slides from the Boreal and Atlantic periods of northeast Switzerland, oocytes of 14 different species and types were identified (of the 45 central European Neorhabdocoela species extant today). Because of their specificity and restriction to certain habitats, Neorhabdocoela oocytes allow the reconstruction of former freshwater quality and lake productivity, and may help us to understand temperature and hydrological changes during the Quaternary.