SCALY INCUNABULA, AUXOSPORE DEVELOPMENT, AND GIRDLE POLYMORPHISM IN SELLAPHORA MARVANII SP. NOV. (BACILLARIOPHYCEAE)

Authors

  • David G. Mann,

    1. Royal Botanic Garden Edinburgh, Edinburgh EH3 3LR, Scotland, UK
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  • Aloisie Poulíčková,

    1. Department of Botany, Faculty of Science, Palacký University, Str. 17. listopadu 1192/12, CZ-771 46 Olomouc, Czech Republic
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  • Shinya Sato,

    1. Royal Botanic Garden Edinburgh, Edinburgh EH3 3LR, Scotland, UK
      Institute of Molecular Plant Sciences, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JH, UK
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  • Katharine M. Evans

    1. Royal Botanic Garden Edinburgh, Edinburgh EH3 3LR, Scotland, UK
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    • Present address: School of Geosciences, University of Edinburgh, Grant Institute, The King’s Buildings, West Mains Road, Edinburgh EH9 3JW, UK.


  • Received 8 September 2010. Accepted 3 May 2011.

Abstract

Uniparental auxosporulation was observed in a monoclonal culture of a Sellaphora clone isolated from the epipelon of a fishpond in the Czech Republic. The cox1 sequence for the clone confirmed that it belonged to the Sellaphora pupula–bacillum species complex but showed significant differences from all previously characterized Sellaphora species, and it is therefore described as S. marvanii sp. nov. Protoplast, valve, and girdle structure resembled those of other Sellaphora species, but a novel finding for all diatoms was a change in girdle structure during the life cycle: the most advalvar girdle band (valvocopula) bore a single line of pores in enlarged postauxospore cells but was entirely plain in small cells and gametangia. The young auxospores were covered by incunabula containing large, delicate, ± circular scales, resembling those of centric diatom auxospores; similar scales have been reported in a few other raphid diatoms (Pseudo-nitzschia multiseries, Diploneis sp.) but contrast with the strip incunabula of some Nitzschia and Pinnularia and the helmet-like caps of Neidium. The scales persisted during auxospore expansion, mostly as two caps over the auxospore poles. The transverse perizonium comprised a very wide, closed primary band, flanked by numerous secondary bands whose open ends were strongly incurved toward the center. Initial valves were differentiated from their immediate descendants by the very strong external demarcation of the raphe sternum, irregular shape, and curved transapical profile.

Ancillary