A new marine araphid diatom, Thalassionema kuroshioensis sp. nov., from temperate Japanese coastal waters

Abstract

A new marine planktonic diatom Thalassionema kuroshioensis sp. nov., was described based on morphological comparison with five other extant Thalassionema species. Thalassionema kuroshioensis was found in coastal to offshore regions of the Kuroshio current in the temperate to subtropical western North Pacific. Morphological characteristics of T. kuroshioensis were identified using light and scanning electron microscopic observations and include isopolar valves, high density of areolae, cross- to club-shaped occluding bars, apical excavations, and sternum traversed across both ends of apices on the valve face. One rimoportula is located at the end of both valve apices connecting with the external opening slit in the deeply excavated apex. The outline of the valve is linear or slightly inflated. We provide size ranges and a key to the species of all known extant Thalassionema species, including the new species.

Keywords:

• Thalassionema
• Thalassionema kuroshioensis sp. nov
• plankton
• cell size
• araphid diatom
• coastal species

Acknowledgements

We thank the anonymous reviewers and the associate editor for their comments which significantly improved the manuscript. Prof. Gustaaf Hallegraeff (University of Tasmania, Australia) is also acknowledged for improving the English and technical terminology. The authors thank the captain, crews and colleagues aboard the R/Vs Hakuho-maru, Tansei-maru, and Soyo-maru for their helpful support at sea. We are grateful to the Nikon Imaging Center at Hokkaido University for technical support with LM observation and to the OPEN FACILITY, Hokkaido University Sousei Hall for technical support with SEM observation.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study was partly funded by the following three projects: ‘Development of simulation techniques to nowcast the biodiversity of marine phytoplankton’ from the Japan Science and Technology Agency and ‘The study of Kuroshio Ecosystem dynamics for sustainable management’ and ‘Establishment of new ecozones in the oceans by meta-genetic community analysis (24121004)’ from the Ministry of Education, Culture, Sports, Science and Technology of Japan.