Five new species in the genus Staurosirella (Bacillariophyta) from European freshwater habitats.

Several populations belonging to the genus Staurosirella have been observed in European rivers that were previously identified as Staurosirellapinnata. In light of the recent taxonomic revisions of the genus Staurosirella, the morphology of the unknown Staurosirella populations has been critically investigated using light and scanning electron microscopy. Following the comparison with previously described Staurosirella species, five taxa could not be identified using the currently available literature on the genus. These five taxa are described as new based on differences in valve outline; shape, size and structure of the apical pore fields; structure of the striae; and the presence, position and structure of the marginal spines. Two new species were described using historic collection material: Staurosirellabinodiformis sp. nov. and Svanheurckiana sp. nov. Two new species were observed in samples from rivers in Flanders: S.marginostriata sp. nov. and S.stoksiana sp. nov. whereas a fifth species was observed in rivers from Iceland: S.jonssoniana sp. nov. All new species are compared with similar Staurosirella species worldwide. Notes are added on their ecological preferences derived from both physicochemical data and the associated diatom flora.