Madinithidium gen. nov. (Bacillariophyceae), a new monoraphid diatom genus from the tropical marine coastal zone

Abstract:

We studied a group of monoraphid diatom species (Bacillariophyceae, Achnanthidiaceae) found in the marine coastal environment of tropical islands of the Caribbean Sea, western Atlantic Ocean, Indian Ocean, South Pacific Ocean, the Adriatic Sea and the Black Sea. Based on light and electron microscope examination, Madinithidium was formally described as a genus new to science with the generitype defined as Madinithidium undulatum. The characteristic features of the valve structure are a strongly developed sternum and raphe sternum, transapical striae formed by a single areola (macroareolae) positioned in small depressions, elevated virgae and coaxial internal central raphe endings. Furthermore, the striae of both raphe and sternum valves are closed by finely perforated hymenes. Madinithidium and Achnanthidium species are difficult to identify correctly with light microscopy since their valves are small and finely structured. Four species recently described from the western Indian Ocean and assigned to Achnanthidium sensu lato – Achnanthidium capitatum, A. flexuistriatum, A. pseudodelicatissimum and A. scalariforme – possessed morphological features permitting their placement into Madinithidium gen. nov. The above-mentioned species were formally transferred to the new genus.

Key Words::

• Achnanthidium
• Achnanthoid diatoms
• Coral reefs
• Madinithidium undulatum
• Martinique Island
• Mascarenes Archipelago

ACKNOWLEDGEMENTS

The authors are grateful to Manfred Ruppel for operating the SEM. This study has been supported by grant no. 2012/04/A/ST10/00544 from the National Science Centre in Kraków and by the ATUPS grant from Université Paul Sabatier. Prof. Kevin McCartney and Dr Thomas G. Bornman helped correct the manuscript's English. We thank Prof. J. Pat Kociolek for critical reading the manuscript and providing valuable remarks, and we thank Agnieszka Kierzek and Genowefa Daniszewska-Kowalczyk for technical assistance. The authors express their gratitude to Ana Car, Dr. Elena Nevrova and Dr Tom Frankovich for providing information on the distribution of Madinithidium species outside of the Mascarenes and the Caribbean Sea.