Diplophrys mutabilis sp. nov., a New Member of Labyrinthulomycetes from Freshwater Habitats

Diplophrys is a ubiquitous protist genus belonging to the class Labyrinthulomycetes. Although most members of Labyrinthulomycetes prefer marine habitats, the genus Diplophrys exclusively consists of the freshwater species Diplophrys archeri and Diplophrys parva. To investigate the genus Diplophrys, several novel strains were isolated from Japanese freshwater environments, and cultures of the strains were established. Among the strains, an organism isolated from Lake Nojiri displayed some characteristic features different from that of both D. archeri and D. parva. Thus, we described this strain as a new species, Diplophrys mutabilis. D. mutabilis can be cultured using dried water flea as food. This species had an orbicular to fusiform shape, and it occasionally penetrated prey with prominent cytoplasm. From a molecular phylogenetic analysis based on 18S rRNA sequences, D. mutabilis evidently belongs to Amphitremida, Labyrinthulomycetes. This study suggests that these species form a unique group in Labyrinthulomycetes.