First record of the genus Decussata (Patrick) Lange- Bertalot (Bacillariophyta) in Serbia – distribution of the rare species D. hexagona (Torka) Lange-Bertalot

The aim of this paper is to present the distribution of Decussata hexagona, a new species in diatom flora of Serbia. Seventy-two diatom samples were collected from six localities along the Vrla and Rasina Rivers during 2011 and 2012. Decussata hexagona was recorded with single specimens or low relative abundance (0.3%) from epilithic communities in seven samples from the Vrla River and in one sample from the Rasina River. It was recorded in unusual epilithic habitats of running neutral to low-alkaline waters with low ion content