Three new species of freshwater Diploneis from Japan

Abstract

Three new Diploneis species are described from freshwater lakes in Japan. A complex wall structure is demonstrated in D. aokiensis sp. nov. and D. yamanakaensis sp. nov., where the basic alternation of transapical ribs (virgae) and striae is overlain by a system of secondary branches and struts supporting the external perforate surface. Diploneis linearifera sp. nov. possesses remarkable external slits, distributed irregularly around the margin of the valve and near the raphe. The grooves in the outer layer of the valve wall, which do not penetrate to the valve interior, have no known parallel in other diatoms but may be related to the angular holes noted previously in D. finnica (Ehrenberg) Cleve and D. marginestriata Cleve.

Keywords:

• Diploneis
• freshwater
• new species
• ribs
• slits
• transapical costae
• valve structure
• virgae

Acknowledgements

Special thanks to Hiromu Kobayasi of Tokyo Diatom Institute for his useful advice, also David G. Mann, Royal Botanic Garden Edinburgh and Mark B. Edlund, Science Museum of Minnesota, for critical reading of the manuscript and helpful comments, and Tamotsu Nagumo of Nippon Dental University for the use of electron microscopy.