Limnetica 38

Dorofeyukea rostellata is a rare and poorly known representative of Dorofeyukea genus. To date, this taxon has only been recorded only outside of Europe. In two Croatian lakes, we found a diatom in appearance similar to Dorofeyukea rostellata and within corresponding physical and chemical conditions. Due to the uncertain taxonomical position of this taxon, type material of Dorofeyukea rostellata and a closely related species, Navicula grimmeioides, were analysed by means of light and scanning electron microscopy. Upon a detailed investigation, we could clearly distinguish the Croatian population from N. grimmeioides. However, the Croatian population and the type material of D. rostellata differed only in minor characteristics. The most obvious difference is the shape of areolae. Nevertheless, differences between the shapes of the areolae can be caused by the degree of silicification, which often depends on the environmental conditions. Since almost every other characteristic of the Croatian population overlapped with that of the type material of D. rostellata we identified it as D. rostellata. Additionally, scanning electron microscopy analyses also revealed that N. grimmeioides belongs to the genus Dorofeyukea, so its new combination was proposed.