Chrysochromulina andersonii sp. nov. (Prymnesiophyceae), a new flagellate haptophyte symbiotic with radiolarians

ABSTRACT

The haptophyte symbiont Chrysochromulina andersonii sp. nov. isolated from the polycystine radiolarian Dictyocoryne truncatum was examined using both natural and cultured materials by light, scanning and transmission electron microscopy as well as molecular phylogenetic analyses of the small subunit (SSU) and large subunit (LSU) rDNA sequences. In culture, the motile cells were saddle-shaped, 3–5 µm long and 3–4 µm wide. They possessed two equal to subequal flagella, a coiling haptonema, and two parietal golden-brown chloroplasts. The scales were arranged in two layers composed of two types: scales with flat rims, 0.19–0.26 µm in diameter, formed the inner layer; whereas, scales with upright rims, 0.25–0.45 µm in diameter, formed the outer layer. Both scales had a faint cross in the centre of the scale face, and the radiating ridges extended from the faint cross to the periphery. Molecular phylogenetic analysis indicated that the SSU and LSU rDNA sequences from our symbiont fell within the clade of Chrysochromulina. However, our symbiont differed in the details of the patterning on the scale face from the other species of Chrysochromulina. Thus, we propose C. andersonii sp. nov. for the symbiotic alga from the polycystine radiolarian D. truncatum.

KEYWORDS:

• Chrysochromulinaceae
• Haptophyta
• Molecular phylogeny
• Polycystines
• Radiolarians
• Symbiont

ACKNOWLEDGEMENTS

We thank the editors and the two anonymous reviewers for critical readings of the article and for providing useful comments and suggestions that helped improve the article. We also thank A. Takemura, S. Harii, Y. Nakano, and S. Kadena of the University of the Ryukyus for their support and helpful discussions.

Additional information

Funding

This study was financially supported by funds from Collaborative Research of Tropical Biosphere Research Center, University of the Ryukyus to T. Yuasa, and by grants-in-aid from JSPS to O. Takahashi (Grant Numbers 18K03821 and 15K05326).