Morphological diversity and phylogeny of the palmelloid chrysophyte genera Chrysotilos and Globulochrysis, gen. nov.

Chrysophytes are a diverse group of stramenopile protists comprising a variety of taxa with different cell organizations. Here, we morphologically and genetically characterize a novel chrysophyte genus isolated from three freshwater localities in the Czech Republic, described as Globulochrysis compacta gen. nov. sp. nov. The genus is well characterized by the frequent formation of closely packed cells, developing into large, spherical sporangia. This alga also forms solitary cells, mucilaginous colonies, amoebae, and teardrop-shaped zoids. We also investigated the morphologically similar genus Chrysotilos, isolated from its type locality in the Austrian Alps. In culture, Chrysotilos showed characteristic neustonic growth, which was, however, not observed in Globulochrysis. Phylogenetic analyses based on 18S rRNA and rbcL genes showed that these two algae belong to two distinct lineages. Whereas Chrysotilos was inferred within the clade Hibberdiales, Globulochrysis formed a completely new lineage within the order Hydrurales. Globulochrysis is described as a new genus in Hydrurales, Chrysophyceae. The genus is characterized by closely packed cells. The phylogenetic position of neustonic Chrysotilos is determined. [ABSTRACT FROM AUTHOR]