An evaluated list of Cenozic-Recent radiolarian species names (Polycystinea), based on those used in the DSDP, ODP and IODP deep-sea drilling programs.

A first reasonably comprehensive evaluated list of radiolarian names in current use is presented, covering Cenozoic fossil to Recent species of the primary fossilising subgroup Polycystinea. It is based on those species names that have appeared in the literature of the Deep Sea Drilling Project and its successor programs, the Ocean Drilling Program and Integrated Ocean Drilling Program, plus additional information from the published literature, and several unpublished taxonomic database projects. 1192 names are recognised as valid, and several hundred additional names including synonyms and mispellings are given as well. A brief list of valid names is provided in the main paper, while the full list, with synonyms, author, year of publication, family assignment, geologic age interval and notes is provided as a SOM spreadsheet table.

Radiolaria associated with large diversity of marine alveolates.

We have isolated cells of unculturable radiolarians from marine coastal waters. Individual cells were subjected to single cell whole genome amplification (SCWGA) and gene-targeted PCR. Using this approach we recover a surprisingly large diversity of sequences related to the enigmatic marine alveolate groups 1 and 2 (MALV I and MALV II) that most likely represent intracellular symbionts or parasites of the radiolarian cells. 18S rDNA phylogeny of the MALV sequences reveals 4 distinct clades of radiolarian associates here named Radiolarian Associated Sequences (RAS) 1-4. One clade of both phaeodarian and radiolarian associates and one clade of only phaeodarian associates are also identified. The MALV sequences cluster according to host type, i.e. sequences from associates identified in radiolarians, fish, copepods, ciliates or dinoflagellates are not intermixed but separated into distinct clades. This implies several independent colonizations of host lineages and links a large diversity of MALV to radiolarian-associated species. This demonstrates that radiolarians may be an important reservoir for MALV, making them a key group for understanding the impact of intracellular symbionts on the marine ecosystem. This study shows that applying SCWGA on unculturable cells is a promising approach to study the vast diversity and interactions of intracellular eukaryote organisms.

Radiolaria divided into Polycystina and Spasmaria in combined 18S and 28S rDNA phylogeny.

Radiolarians are marine planktonic protists that belong to the eukaryote supergroup Rhizaria together with Foraminifera and Cercozoa. Radiolaria has traditionally been divided into four main groups based on morphological characters; i.e. Polycystina, Acantharia, Nassellaria and Phaeodaria. But recent 18S rDNA phylogenies have shown that Phaeodaria belongs within Cerocozoa, and that the previously heliozoan group Taxopodida should be included in Radiolaria. 18S rDNA phylogenies have not yet resolved the sister relationship between the main Radiolaria groups, but nevertheless suggests that Spumellaria, and thereby also Polycystina, are polyphyletic. Very few sequences other than 18S rDNA have so far been generated from radiolarian cells, mostly due to the fact that Radiolaria has been impossible to cultivate and single cell PCR has been hampered by low success rate. Here we have therefore investigated the mutual evolutionary relationship of the main radiolarian groups by using the novel approach of combining single cell whole genome amplification with targeted PCR amplification of the 18S and 28S rDNA genes. Combined 18S and 28S phylogeny of sequences obtained from single cells shows that Radiolaria is divided into two main lineages: Polycystina (Spumellaria+Nassellaria) and Spasmaria (Acantharia+Taxopodida). Further we show with high support that Foraminifera groups within Radiolaria supporting the Retaria hypothesis.

Molecular diversity of alveolates associated with neritic north atlantic radiolarians.

Seven species of polycystine radiolarians and one phaeodarian species were investigated in order to determine the diversity of their associate organisms and their species specificity. Twelve partial 18S ribosomal DNA (rDNA) sequences were obtained showing a high diversity of associates, both within spumellarian and nassellarian radiolarians and among species. Two of the sequences obtained are highly similar to Scrippsiella, a dinoflagellate genus already reported as a symbiont of polycystine radiolarians. Nine of the new 18S rDNA sequences group with various alveolates. Some of these groups include parasites, such as the lethal endoparasite Amoebophrya, while others consist of non-annotated novel organisms found worldwide in various types of marine environments. We also obtained a sequence from a bacillariophytan highly similar to the 18S rDNA of the diatom species Diatoma tenue, which may derive from radiolarian food. Additionally, this is the first study to report on a phaeodarian associate.