A detailed study of desmid flora was performed during 1997–1998 in the Dubičiai bog lakes (southeast of Lithuania), which had never been investigated by phycologists. The studies revealed 181 desmid taxa of which 27 are new to Lithuania. This paper is the first part of the material on new desmid species and contains information on morphometrics and the ecology data of five taxa: Pleurotaenium eugeneum, P. nodosum, Xanthidium armatum, Staurodesmus spencerianus, and Desmidium grevillei.
Keywords: desmids, lakes, bog, Dubičiai, southeast Lithuania.