Morphological and molecular investigation on freshwater choanoflagellates (Craspedida, Salpingoecidae) from the River Rhine at Cologne (Germany).

Paramonosiga coloniensis sp. nov., Salpingoeca amphoriscia sp. nov., S. fluviatilis sp. nov. and S. loutrophoria sp. nov. are frequently found craspedid species in the River Rhine which have not yet been described, despite their high abundance. All new species are characterized based on a distinct morphology which is different from all up to now described species and on a molecular level based on transcriptome data. In addition, we give extended redescriptions of S. amphoridium and S. angulosa, based on SSU and LSU rDNA data and morphology. The six-gene phylogenetic analyses place all species into freshwater clades of the craspedids. The separation of the freshwater and marine clades of this group is becoming more distinct with every craspedid sequence added. The River Rhine is one of the largest rivers in Europe but its protist biodiversity is fairly undescribed, especially regarding choanoflagellates. We conclude that the biodiversity of craspedid choanoflagellates is broadly underestimated.