Valve ultrastructure of two new genera of marine canal-bearing diatoms (Bacillariophyceae)

Abstract

Witkowski A., Kociolek J.P. and KurzydŁowski K.J. 2011. Valve ultrastructure of two new genera of marine canal-bearing diatoms (Bacillariophyceae). Phycologia 50: 170–181. DOI: 10.2216/09-103.1

In this paper we propose two new genera, Archibaldia Witkowski & Kociolek and Nagumoea Kociolek & Witkowski, for the species originally included in Gomphonitzschia (Gomphonitzschia capensis Giffen) and Denticula (Denticula neritica Holmes & Croll), respectively. Our proposal is based on the detailed analysis of ultrastructure of three species, G. capensis Giffen, Nagumoea neritica Witkowski & Kociolek (=D. neritica), and a third species resembling N. neritica. A review of these taxa, with light and scanning electron microscopy, reveals robust fibulae and portules, characteristic of canal raphe-bearing diatoms, but no elevated keel is present on the external valve face. Superficially these taxa appear similar to one another on the basis of the structure of the canal raphe, sparse ornamentation, and types of areolae on the valves. These taxa are compared with members of the Bacillariales Hendey with which they share the canal raphe. They differ with regard to raphe structure, though they share similarities with certain taxa that lack keels. The new genera are placed in the Bacillariales, pending a further review of the systematic relationships within this group.

Key Words::

• Archibaldia
• Bacillariales
• Canal-bearing diatoms
• Marine species
• Nagumoea
• New genera

ACKNOWLEDGEMENTS

The authors are grateful to following colleagues for help and assistance during the study: Manfred Ruppel, J.W. Goethe University in Frankfurt am Main, Germany, and Scott Serata, California Academy of Sciences, for operating the SEM; Dr Tomasz Płociński for his help with SEM/TEM; Dr Ewa Borowiak, Western Pomeranian University of Technology for her help with TEM; Gideon P. Kriel for help in collecting the literature; Tsuyoshi Watanabe for the assistance with LM microphotographs; Agnieszka Kierzek with preparation of the plates; and Colin Archibald for help with sampling from the marine littoral in South Africa. The type slide of D. neritica was received as a loan from the Diatom Collection of the Natural History Museum of London. The authors are grateful to the South African National Parks administration for permission to sample diatoms in the Saldanha Bay area of South Africa. We appreciate the advice provided by Dr Wolf Henning Kusber regarding the nomenclatural status of Denticula neritica.