Oricymba (Cymbellales, Bacillariophyceae), a new cymbelloid genus and three new species from the Nepalese Himalaya

Abstract

Jüttner I., Krammer K., Van de Vijver B., Tuji A., Simkhada B., Gurung S., Sharma S., Sharma C. and Cox E.J. 2010. Oricymba (Cymbellales, Bacillariophyceae), a new cymbelloid genus and three new species from the Nepalese Himalaya. Phycologia 49: 407–423. DOI: 10.2216/09-77.1

A new genus Oricymba is described with its type species based on Cymbella japonica Reichelt. In addition, three new species are described from the Nepalese Himalaya: O. subaequalis, O. latirotundata and O. subovalis. The new genus has slightly dorsiventral or almost symmetrical valves with polar raphe endings deflected to the dorsal side. It can be distinguished from other cymbelloid genera by two morphological characters. There is a ridge along the valve face: mantle junction, and areolae are slit-like and partially occluded by dentate projections. To date Oricymba has been found only in often nutrient-poor, freshwater habitats of the Indian subcontinent, Southeast Asia, Korea and Japan.

Key Words::

• Asia
• Cymbella japonica
• Cymbellales
• Diatoms
• Nepal
• New genus
• Oricymba

ACKNOWLEDGMENTS

We thank Friedel Hinz, Alfred-Wegener-Institut für Polar- und Meeresforschung, Bremerhaven, for providing the type material of Cymbella japonica and C. subalpina and Ruth Nielsen, Botanic Garden & Museum, Natural History Museum, University of Copenhagen, for providing the type material of Cymbella sabzewarensis; Som G. Chhetri, Himalayan Nature, Kathmandu, for technical assistance in the field; Phil Brewin, Cardiff University, for fieldwork in the Arun catchment; Jim Chimonides, Department of Zoology, The Natural History Museum, London, for help with the maps; Roger Wyatt, Jeremy Wilkinson, Alan Jenkins, NERC Centre for Ecology and Hydrology, Wallingford, and Vic Din, Gary Jones, Department of Mineralogy, The Natural History Museum, London, for the water chemistry analyses; Dick Johnson, NERC Centre for Ecology and Hydrology, Wallingford, for organising the trek in 1994; Steve Ormerod, Cardiff University, for providing River Habitat Survey data; Marcel Verhaegen and Myriam de Haan, National Botanic Garden of Belgium, Meise, for technical assistance with the SEM; and two anonymous reviewers for their comments on the manuscript. This research received support from the EU Synthesys project, WWF Nepal, and an EU Marie Curie Fellowship to IJ (held at The Natural History Museum).