Species of the Cocconeis peltoides group with a marginal row of unusual processes (Mascarenes and Kerguelen Islands, Indian Ocean)

Abstract

Two diatoms related to Cocconeis peltoides Hustedt (Bacillariophyceae), from coral reef environments (Mascarenes, Western Indian Ocean), are proposed as a new Cocconeis variety and a new C. species: Cocconeis peltoides var. archaeana Riaux-Gobin et Compère and Cocconeis sigillata Riaux-Gobin et Al-Handal. Cocconeis peltoides and the two new taxa possess an unusual marginal row of small processes on their sternum valve, internally opening as curb-like structures. Several other Cocconeis species, encountered during sampling campaigns in Kerguelen (Southern Ocean, Indian Ocean sector), also share such processes, including Cocconeis hauniensis Witkowski and Cocconeis germainii Riaux-Gobin, Witkowski et Romero. The shared characteristics of these taxa are examined and compared in detail.

Keywords:

• benthic diatoms
• Cocconeis peltoides
• Indian Ocean
• marginal processes

Acknowledgements

Thanks are due to Bart Van de Vijver for drawing our attention to the resemblance of the SV of our Cocconeis peltoides with Catillus subimpletus and for his help with the LM illustration. We are grateful to Dimitri Gorand (C2M, University of Perpignan Via Domitia) for SEM assistance. Many thanks are also due to an anonymous reviewer for his helpful comments and English revision, and to Mario De Stefano for his constructive remarks. C.R.-G. also thanks ‘Naturalia & Biologia’ and the ‘Centre National de la Recherche Scientifique’ (CNRS) for funding diatom studies at the Mascarenes. ‘Terres Australes et Antarctiques Françaises’ (TAAF) are also acknowledged for funding studies at the Kerguelen Islands, and Bibliotheca Diatomologica and J. Cramer for giving permission to reproduce figure 47, which appeared in volume 47 (pl. 42, fig. 5).