, a new member of the holocarpic parasitoid genus from the invasive freshwater diatom .

Holocarpic oomycetes are poorly known but widespread parasites in freshwater and marine ecosystems. Most of the holocarpic species seem to belong to clades that diverge before the two crown lineages of the oomycetes, the and the . Recently, the genus was described to accommodate , a holocarpic parasitoid of diatoms, which received varying support for its placement as the earliest-diverging oomycete lineage. In the same phylogenetic reconstruction, was grouped with some somewhat divergent sequences derived from environmental sequencing, indicating that would not remain monotypic. Here, a second species of is reported, which was found as a parasitoid in the limnic centric diatom . Its life-cycle stages are described and depicted in this study and its phylogenetic placement in the genus revealed. As a consequence, the newly discovered species is introduced as .