The systematics of Zoochlorella revisited employing an integrative approach |
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Authors: | Thomas Pröschold Tatyana Darienko Paul C. Silva Werner Reisser Lothar Krienitz |
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Affiliation: | 1. Culture Collection of Algae and Protozoa, Scottish Association for Marine Science, Argyll, Scotland, UK.;2. University of Vienna, Department of Limnology, Althanstr. 14, A‐1090 Wien (Vienna), Austria.;3. M.G. Kholodny Institute of Botany on National Academy Science of Ukraine, Kyiv 01601, Ukraine.;4. University Herbarium, University of California, Berkeley, California 94720‐2465, USA.;5. University Leipzig, Institute of Biology I, D‐04103 Leipzig, Germany.;6. Leibniz‐Institute of Freshwater Ecology and Inland Fisheries, D‐16775 Stechlin‐Neuglobsow, Germany. |
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Abstract: | ![]() Symbiosis of green algae with protozoa and invertebrates has been studied for more than 100 years. Endosymbiotic green algae are widely distributed in ciliates (e.g. Paramecium, Stentor, Climacostomum, Coleps, Euplotes), heliozoa (e.g. Acanthocystis) and invertebrates (e.g. Hydra, Spongilla), and have traditionally been identified as named or unnamed species of Chlorella Beij. or Zoochlorella K. Brandt or referred to as Chlorella‐like algae or zoochlorellae. We studied 17 strains of endosymbionts isolated from various hosts and geographical localities using an integrative approach (nuclear encoded small subunit and internal transcribed spacer regions of rRNA gene sequences including their secondary structures, morphology, physiology and virus sensitivity). Phylogenetic analyses have revealed them to be polyphyletic. The strains examined belong to five independent clades within the Trebouxiophyceae (Choricystis‐, Elliptochloris‐, Auxenochlorella‐ and Chlorella‐clades) and Chlorophyceae (Scenedesmus‐clade). The most studied host organism, Paramecium bursaria, harbours endosymbionts representing at least five different species. On the basis of our results, we propose a taxonomic revision of endosymbiotic ‘Chlorella’‐like green algae. Zoochlorella conductrix K. Brandt is transferred to Micractinium Fresen. and Zoochlorella parasitica K. Brandt to Choricystis (Skuja) Fott. It was shown that Choricystis minor (Skuja) Fott, the generitype, is a later heterotypic synonym of Choricystis parasitica (K. Brandt) comb. nov. A new species, Chlorella heliozoae, is proposed to accommodate the endosymbiont of Acanthocystis turfacea. |
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