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Protists (eukaryotes, excluding animals, land plants, and fungi) comprise the bulk of the eukaryotic phylogenetic tree, making their diversity essential to understanding eukaryotic evolution. Nevertheless, they remain understudied due to their microscopic size and difficulty in cultivation.

Researchers at the University of Tsukuba have successfully established a culture strain of a protist from a seaweed sample collected from a marine lake in the Republic of Palau. Microscopic observations revealed that this organism is a new species of the genus Glissandra, whose phylogenetic position was uncertain, and the researchers named it Glissandra oviformis.

Large-scale molecular phylogenetic analysis based on 340 protein sequences revealed that G. oviformis is a novel lineage within CRuMs, one of the major eukaryotic lineages. To elucidate the evolution of morphological traits within CRuMs, the researchers examined G. oviformis under an electron microscope, which revealed that the sheet-like structure lining the cell membrane and the structure of the base of the flagella are common with those of CRuMs members.

These observations, now in Open Biology, revealed shared characteristics among CRuMs members. The rediscovery, culturing, and detailed investigation of protists with uncertain phylogenetic positions could be an essential approach to understanding the evolution of eukaryotic organisms.