Peridiniopsis jiulongensis, a new freshwater dinoflagellate with a diatom endosymbiont from China

Detailed study on Peridiniopsis species using modern techniques is still limited. Here we report a new Peridiniopsis species isolated from the Jiulong River, China, which was described as jiulongensis H. Gu sp. nov. Vegetative cells of P. jiulongensis were subjected to detailed examination by light microscopy, scanning electron microscopy and transmission electron microscopy. P. jiulongensis has a plate pattern of Po, X, 3', la, 6 '', 5C, 5S, 5''',, 2 '''' and harbors a dinokaryotic and a eukaryotic nucleus. The eyespot of P. jiulongensis was bounded by triple envelopes and thus classified as type D. Molecular phylogeny based on dinoflagellate small subunit ribosomal DNA (SSU rDNA) sequences revealed that dinoflagellates with a diatom endosymbiont were monophyletic and P. jiulongensis was grouped together with Peridiniopsis cf. kevei, P niei and P. penardii. Molecular phylogeny based on endosymbiont SSU rDNA sequences showed that P. jiulongensis, P. cf. kevei, and P. penardii formed a well resolved group and were close to Thalassiosira species.