The Katablepharids are a Distant Sister Group of the Cryptophyta: A Proposal for Katablepharidophyta Divisio Nova/Kathablepharida Phylum Novum Based on SSU rDNA and Beta-Tubulin Phylogeny

Abstract

The katablepharids are a morphologically well-defined group of heterotrophic flagellates. Since their original description in 1939, they have been classified in the Cryptophyceae (Cryptophyta) based on their similar cell shape, flagellar orientation, and the presence of ejectisomes visible by light microscopy. However, electron microscopy suggests that the katablepharids are distinct from cryptomonads. A possible affinity with the Alveolata has been proposed which is mainly based on the resemblance of their feeding apparatus to the apical complex of the Apicomplexa or to the tentacles of the Ciliophora. In this study, we provide the first SSU rDNA and beta-tubulin molecular sequence data for two katablepharids: Katablepharis japonica sp. nov. and Leucocryptos marina. We reveal that the katablepharids are not closely related to the Alveolata; rather, phylogenetic reconstruction analyses of SSU rDNA and beta-tubulin suggest that the katablepharids are a distant sister group of the Cryptophyta. We therefore conclude that the katablepharids should be a group equivalent to the Cryptophyta and propose Katablepharidophyta divisio nova (ICBN)/Kathablepharida phylum novum (ICZN).