title: Ultrastructure and LSU rDNA-based phylogeny of Peridinium lomnickii and description of Chimonodinium gen. nov. (Dinophyceae).
abstract: Several populations of Peridinium lomnickii were examined by SEM and serial section TEM. Comparison with typical Peridinium, Peridiniopsis, Palatinus and Scrippsiella species revealed significant structural differences, congruent with phylogenetic hypotheses derived from partial LSU rDNA sequences. Chimonodinium gen. nov. is described as a new genus of peridinioids, characterized by the Kofoidian plate formula Po, cp, x, 4', 3a, 7'', 6c, 5s, 5''', 2'''', the absence of pyrenoids, the presence of a microtubular basket with four or five overlapping rows of microtubules associated with a small peduncle, a pusular system with well-defined pusular tubes connected to the flagellar canals, and the production of non-calcareous cysts. Serial section examination of Scrippsiella trochoidea, here taken to represent typical Scrippsiella characters, revealed no peduncle and no associated microtubular strands. The molecular phylogeny placed C. lomnickii comb. nov. as a sister group to a clade composed of Thoracosphaera and the pfiesteriaceans. Whereas the lack of information on fine structure of the swimming stage of Thoracosphaera leaves its affinities unexplained, C. lomnickii shares with the pfiesteriaceans the presence of a microtubular basket and the unusual connection between two plates on the left side of the sulcus, involving extra-cytoplasmic fibres.
authors.affiliation: GeoBioSciences, GeoTechnologies and GeoEngineering (GeoBioTec) Research Unit and Department of Biology, University of Aveiro, P-3810-193 Aveiro, Portugal.
authors.forename: Sandra C
authors.initials: SC
authors.lastname: Craveiro
authors.forename: António J
authors.initials: AJ
authors.lastname: Calado
authors.forename: Niels
authors.initials: N
authors.lastname: Daugbjerg
authors.forename: Gert
authors.initials: G
authors.lastname: Hansen
authors.forename: Øjvind
authors.initials: Ø
authors.lastname: Moestrup
mesh_terms: D056893:Alveolata / Q000145:classification* / Q000235:genetics / Q000648:ultrastructure*; D016000:Cluster Analysis; D016054:DNA, Protozoan / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D020459:Genes, rRNA; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D008969:Molecular Sequence Data; D015388:Organelles / Q000648:ultrastructure; D010802:Phylogeny; D016053:RNA, Protozoan / Q000235:genetics; D012335:RNA, Ribosomal / Q000235:genetics; D017422:Sequence Analysis, DNA
chemical_list: D016054:DNA, Protozoan; D004275:DNA, Ribosomal; D016053:RNA, Protozoan; D012335:RNA, Ribosomal; C065096:RNA, ribosomal, 26S