A rediscovery of Cymbella mirabilis Hustedt, a rare endemic diatom, and description of Alveocymba gen. nov.

Abstract

The first comprehensive morphological investigation of the rare, endemic species Cymbella mirabilis Hustedt from the Malili lake system (Indonesia) was prepared using recent samples. This species was originally described on the basis of a single valve. The species was assigned to Cymbella sensu lato on the basis of its asymmetry about the apical axis. SEM investigation shows that this species has a number of unique features relative to other freshwater cymbelloid diatoms, such as an axial plate and marginal laminae on either side of the valve and pseudoseptum at each end of the valve. In these features C. mirabilis resembles certain species in genera such as Gomphoneis Cleve, Afrocymbella Krammer, Gomphosinica Kociolek et al. and Gomphonema Ehrenberg. The unique combination of features in this taxon suggest it cannot be placed in any known genus within the Cymbellales. Thus, we describe a new diatom genus, Alveocymba gen. nov., however, the taxonomic placement of this new genus remains unclear and requires further investigation.

Keywords:

• Alveocymba
• Cymbella
• diatom
• Indonesia
• morphology
• new genus
• taxonomy

Acknowledgements

We are grateful to the staff of the Center of Collective Use of Electron Microscopy of Papanin Institute for the Biology of Inland Waters, Russian Academy of Science for providing the scanning electron microscopy study. This publication is based on research carried out with financial support by Russian Science Foundation (19–14–00320) for LM and sample investigation, by the Russian President Foundation (M-1446.2020.4) for SEM, and by framework of the state assignment (theme AAAA–A19–119041190086–6) for completing the manuscript. We appreciate the constructive remarks of E. Cox for her important insights on the phylogeny and taxonomy of this new genus and for editorial corrections.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The study was supported by the Russian Science Foundation (project №19-14-00320).