Morphological investigation and transfer of Naviculadicta parasemen Lange-Bertalot to the genus Rexlowea Kociolek & Thomas

Abstract

We document the size diminution series and valve morphology of the diatom Naviculadicta parasemen Lange-Bertalot in Lange-Bertalot & Genkal, described originally from the Yugorsky Peninsula and nearby islands, northwest Siberia. Based on material from the northeastern Arctic, the features of the valve structure, undulate raphe with dilated external proximal raphe ends, organization of the striae, and change in orientation of the striae near the apices suggest a close affinity with the monotypic genus Rexlowea. We effect the transfer of N. parasemen to Rexlowea, making the new combination R. parasemen. Several features of R. navicularis, the generitype, are missing from R. parasemen, including septa and pseudosepta. It may therefore be necessary to emend the description of Rexlowea as additional species are referred to the genus, but we will await discovery of additional species before formal emendation.

Keywords:

• diatoms
• Rexlowea
• new combination
• Arctic
• freshwater

Acknowledgements

The authors thank Manfred Ruppel for the SEM images.

Additional information

Funding

This publication is based on research carried out with financial support by Russian Science Foundation (14-14-00555).