Morphology and phylogenetic position of a rare four-celled green alga, Pascherina tetras (Volvocales, Chlorophyceae), based on cultured material
2015
Since the original description in 1928, four-celled colonies of the spondylomoracean genus Pascherina have not been studied in detail due to a lack of reliable culture strains of this genus for reexamination and molecular phylogenetic analyses. Here, we established new culture strains of Pascherina tetras, the only species of the genus, from Japanese samples and conducted detailed light and transmission electron microscopic observations and a molecular phylogenetic analysis based on the strains. The light microscopic features of the Japanese material were consistent with those of the original material collected in Ukraine, except for the stigma of the chloroplast; the stigma of the Japanese strains was ring-shaped based on a surface view. The ring-shaped stigma was confirmed by transmission electron microscopy. Our molecular phylogenetic analysis revealed that Pascherina was robustly separated from the other three colonial volvocalean lineages: Stephanosphaera (Haematococcaceae), colonial volvocine algae and Pyrobotrys (Spondylomoraceae). The present morphological and molecular analyses represent the first study to demonstrate the polyphyly of Spondylomoraceae.
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