Gymnochlora dimorpha sp nov., a chlorarachniophyte with unique daughter cell behaviour
Résumé
A new chlorarachniophyte species, Gymnochlora dimorpha sp. nov., was described. This new species was isolated from an enrichment preculture of Padina sp. collected from a subtidal coral reef zone in Republic of Palau. The new strain, P314, was characterized by light and electron microscopy in the present study. Under the culture conditions used here, the amoeboid stage was dominant. Two types of amoeboid cells were found in the cultures: motile and flattened nonmotile (sessile) cells: The motile cells typically multiplied via binary cell division. The sessile cells were always present in the cultures, but they never became dominant under the culture conditions. Time-lapse video microscopic observations revealed that after cell division of a sessile cell, one daughter cell became motile, while the other remained sessile. According to ultrastructural characteristics of the pyrenoids and nucleomorphs, the new chlorarachniophyte strain belongs to the genus Gynmochlora. However, P314 differed from G. stellata, the only hitherto known species of that genus, by forming flattened sessile cells in culture and having smaller cell dimensions (7-14 mu m). Therefore, P314 is described here as a new species of Gymnochlora. This conclusion is supported by previously reported 18S rDNA phylogenies of chlorarachniophytes. The genus Gymnochlora as defined by morphology accorded with the molecular phylogenies.