Morphology, reproduction and taxonomy of Volvox dissipatrix (Chlorophyceae) from Thailand, with a description of Volvox zeikusii sp. nov.

ABSTRACT

A strain of Volvox collected from Thailand produced a very large asexual spheroid with maximum diameter over 2 mm long. This Thai alga was identified as Volvox dissipatrix based on the delicate cytoplasmic bridges between somatic cells, gelatinous matrix structure, monoecious sexual spheroids and the original description reporting the large asexual spheroids. Comparative analyses of light and electron microscopic features and internal transcribed spacer 2 sequences of the nuclear ribosomal DNA of Thai and Australian monoecious strains of V. dissipatrix and their closely related heterothallic strains demonstrated that the latter represents a new species, Volvox zeikusii Nozaki.

KEYWORDS:

• Heterothallic species
• Homothallic species
• Molecular phylogeny
• Sexuality
• Somatic cell
• Transmission electron microscopy

ACKNOWLEDGEMENTS

We are grateful to Professor Emeritus David L. Kirk (Washington University in St. Louis), who kindly sent Volvox dissipatrix strain Marb. 2RS 29 and its valuable information to H.N. Thanks are also due to Dr. Sujeephon Athibai (Khon Kaen University) for her kind help during our field collection in Thailand.

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Funding

This work was supported by Grants-in-Aid for Scientific Research (Nos. 25304012 and 16H02518 to HN) from MEXT/JSPS KAKENHI.