1. Department of Biology, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerpen, Belgium, MARE Center, Laboratory for Oceanology, Liège University, B6, B-4000, Liège, Belgium, Nucleoside Research and Mass Spectrometry Unit, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk, Belgium, and Department of Pathology, Faculty of Veterinary Medicine, Liège University, B43, B-4000 Liège, Belgium