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

ABSTRACT

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.

Highlights

• 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.

KEYWORDS:

• Chrysophytes
• freshwater algae
• neustonic growth
• phylogeny
• sporangia
• taxonomy

Acknowledgements

We thank Santina Soru for providing the drawing of the holotype, Robert Andersen for valuable discussions, and Natálie Čížková, Petr Knotek, Jana Schmidtová, Kateřina Tučková and Veronika Veselá for their support with Chrysotilos sampling.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

The following supplementary material is accessible via the Supplementary Content tab on the article’s online page at https://doi.org/10.1080/09670262.2024.2340026.

Supplementary table S1. List of sequences analyzed in this study, with classification, accession numbers, and affiliation to different alignment datasets.

Supplementary data S1. Video of Chrysotilos ferrea by LM. This video shows the zoospores tended to spin in small circles.

Supplementary data S2. Video of Globulochrysis compacta by LM. This video shows filopodia.

Author contributions

V. Malavasi: obtaining the morphological data, sequencing, assembling figure panels, drafting and editing manuscript; M. Pusztai: culture experiments, drafting and editing manuscript; I. Jadrná: isolation of algal strains, sequencing; Z. Škvorová: isolation of algal strains, sequencing; P. Škaloud: conceiving the study, phylogenetic analyses, drafting and editing manuscript and funding acquisition.

Additional information

Funding

The study was supported by the Czech Science Foundation [project No. 20-22346S].