A research group led by Assistant Professor Shunshi Shiratori of the University of Tsukuba has rediscovered the rare marine amoeba ``Rhabdamoeba marina,'' of which only two cases have been reported in the past 100 years, in seawater collected from the coast of Tottori Prefecture.By cultivating it and analyzing its gene sequence, the systematic position of this mysterious amoeba was revealed for the first time, and based on the results, a new taxonomic treatment was proposed.
Rhabdamoeba marina (R. marina) is a small marine amoeba discovered and described in England in 1921. The amoeboid cells of R. marina are almost immobile, and when surrounding food becomes scarce, the amoebocytes generate flagellated cells with two backwardly extending flagella by budding.Such characteristics are not seen in other amoebas, and there have been only two reports including the original description, and the taxonomic treatment has not been sufficiently verified.
In this research, we succeeded in establishing a cultured strain of R. marina from seawater collected from the coast of Tottori Prefecture.As a result of optical microscopic observation, it was concluded that it was R. marina because the characteristics matched with known characteristics.Furthermore, electron microscopy revealed for the first time a rod-shaped structure called an injection device at the tip of the pseudopod.
Furthermore, when the gene sequence was obtained and analyzed, it was found that it is not included in the taxonomic group that it was previously thought to belong to, but is closely related to the chlorarachnion algae of the phylum Cercozoa.Therefore, we proposed to classify R.marina into the class Chlorarachnion.
Through this research, the gene sequence of R. marina, a rare amoeba that has rarely been discovered until now, was obtained for the first time, and its phylogenetic position was clarified.There are many such single-celled organisms whose phylogenetic positions are unknown due to the lack of research, and rediscovering them through careful observation of environmental samples is essential to understanding microbial diversity.
Paper information:【The Journal of Eukaryotic Microbiology】Rhabdamoeba marina is a heterotrophic relative of chlorarachnid algae
