Ultrastructure and phylogeny of <i>Parietochloris toyamaensis</i> sp. nov. and <i>P. bilobata</i> (Trebouxiophyceae)

We describe <i>Parietochloris toyamaensis</i> sp. nov. and verify the taxonomic status of <i>P. bilobata</i> (originally described as <i>Neochloris</i> and once combined with <i>Ettlia</i>), using ultrastructural and molecular analyses. <i>P. toyamaensis</i> was isolated from soil collected in Toyama, Japan. It had a parietal chloroplast with pyrenoids that were discontinuously covered with starch segments and penetrated more or less in parallel by thylakoid membranes, and reproduced by forming naked, somewhat dorsoventral, biflagellate zoospores. Two contractile vacuoles were in line lengthwise, located in the median ventral side of the zoospores, as in the type <i>P. alveolaris</i>. The basal apparatus components included a single microtubule in the dexter root. <i>P. toyamaensis</i> was separately resolved from other members of the genus in the 18S rDNA and ITS2 trees. Since the authentic strain ASIB V141 of <i>P. bilobata</i> (stored as <i>Ettlia</i>) has been lost, ASIB V143 was used as a reference in place of it. <i>P. bilobata</i> ASIB V143 was resolved in the ‘<i>Parietochloris</i> sensu stricto’ clade but not ‘<i>Lobosphaera</i>’ clade in the 18S rDNA tree, so taxonomically the combination of <i>N. bilobata</i> with <i>Parietochloris</i> as <i>P. bilobata</i> by Andreyeva was confirmed. In zoospores of the strains of <i>P. bilobata</i>, contractile vacuoles were located in the ventral side, as in <i>P. alveolaris</i>. The taxonomic relationship between <i>P. bilobata</i> and <i>P. grandis</i>, and evaluation of the unique position of contractile vacuoles in dorsoventral zoospores as one of the key characters of <i>Parietochloris</i> were discussed. Characterization of the species of <i>Parietochloris</i> by using ultrastructural and molecular data.Proposal of <i>Parietochloris toyamaensis</i> sp. nov.Verification of phylogenetic position of <i>Parietochloris bilobata.</i> Characterization of the species of <i>Parietochloris</i> by using ultrastructural and molecular data. Proposal of <i>Parietochloris toyamaensis</i> sp. nov. Verification of phylogenetic position of <i>Parietochloris bilobata.</i>