Molecular diversity of endosymbiotic Nephroselmis (Nephroselmidophyceae) in Hatena arenicola (Katablepharidophycota)

Hatena arenicola (Katablepharidophycota) is a single-celled eukaryote that temporarily possesses a chlorophyte alga of the genus Nephroselmis as an intracellular symbiont. In the present study, we investigated the molecular diversity of the endosymbiont Nephroselmis in a natural population of the host H. arenicola . We sequenced the host’s 18S rRNA gene and the endosymbiont’s plastid-encoded 16S rRNA gene. The results indicated that almost identical strains of the host harbored at least three distinct strains of the algal endosymbiont affiliated to the clade Nephroselmis rotunda . This finding supports our previous hypothesis that H. arenicola and its symbiotic alga are in an early stage of secondary endosymbiosis.