Ultrastructure of Diatomella balfouriana with a discussion of septum-like structures in diatom genera

Abstract

The ultrastructure of Diatomella balfouriana Greville collected from Île de la Possession, a sub-Antarctic island in the Crozet Archipelago, was studied using high-resolution scanning and transmission electron microscopy. The alveolate striae of the genus are subdivided by small vimines, presenting a unique feature never observed before in other diatom genera. The most striking feature of the genus is the presence of the septum-like structures projecting from the girdle bands. The term scalariform valvocopula is introduced for these structures to discriminate them from the septa present in several araphid and (at least one) raphid genera. The taxonomic position of the genus within the family Pinnulariaceae D.G. Mann is discussed based on the study of the structure of the alveolate striae.

Keywords:

• ultrastructure
• Diatomella
• taxonomic position
• septum-like structure
• scalariform valvocopula

Acknowledgements

This study was supported by an EU Synthesys grant to BVDV to visit the National History Museum in London, UK. We are grateful to A. Ball and the staff of the EMMA laboratory at the Natural History Museum for their assistance with the scanning electron microscopy. The comments of two anonymous reviewers greatly improved this paper.