Morphology And Phylogeny Ofthecadinium Ovatum(Dinophyceae) From The Pacific Coast Of Russia

Thecadinium ovatumis one of the four species ofThecadinium sensu latowhich has no apical pore, but has a ventral pore on the first apical plate, an unusual 'multi-pimple-plate' in the precingular series, and an antapical plate with several spines. Its original thecal plate formula was 3MODIFIER LETTER PRIME 6MODIFIER LETTER PRIMEMODIFIER LETTER PRIME 6c 5s? 5MODIFIER LETTER PRIMEMODIFIER LETTER PRIMEMODIFIER LETTER PRIME 1MODIFIER LETTER PRIMEMODIFIER LETTER PRIMEMODIFIER LETTER PRIMEMODIFIER LETTER PRIME. Morphological examination of cells from the Sea of Japan showed thatT. ovatumhas four apical plates and that the multi-pimple-plate is an anterior intercalary plate. The revised thecal plate formula of the species is 4MODIFIER LETTER PRIME1a 5MODIFIER LETTER PRIMEMODIFIER LETTER PRIME6c 6s 5MODIFIER LETTER PRIMEMODIFIER LETTER PRIMEMODIFIER LETTER PRIME1MODIFIER LETTER PRIMEMODIFIER LETTER PRIMEMODIFIER LETTER PRIMEMODIFIER LETTER PRIME. Molecular genetic data ofT. ovatumwere obtained for the first time. LSU rRNA gene sequences obtained by a single-cell PCR method from natural samples were used for taxonomic and phylogenetic studies. The sequence forT. ovatumdid not show a close phylogenetic relationship to sequences ofT. yashimaense, T. kofoidiiandT. pseudokofoidii. The phylogenetic analysis of the D1/D2 and D8/D10 regions of the large subunit (LSU) rRNA from single cells indicated thatThecadinium ovatumformed the nearest sister branch to the Protoceratiaceae, includingPentaplacodinium usupianum, Pentaplacodinium saltonense, Protoceratium reticulatum, andCeratocorysspecies. This clade was placed within the order Gonyaulacales. Consequently,T. ovatumdoes not belong toThecadinium sensu stricto, nor does it show a phylogenetic relationship with otherThecadinium sensu latospecies (T. yashimaenseandPsammodinium inclinatum). Thus,T. ovatumshould be transferred to an independent new genus that may be created after genetic information is available for the other morphologically close species.